Former Princeton Public Schools Enrollment Committee member questions integrity of district enrollment forecast

By Jian Chen

Dear Neighbors,

If the large turnout at the Princeton Public Schools community forum was any indication, the community seems anxious to learn about how future enrollment will look like from the professionals at Milone & MacBroom that the taxpayers paid $144,000 for. As someone who has closely followed this issue and crunched the numbers over the past two years, I’d like to take this opportunity to share with you some of my thoughts. But I’d like to preface this letter by stating that “writing to newspaper” is not my preferred way to communicate with our school district leadership on this subject. That was why I wrote to the superintendent and the board multiple times in the summer of 2018 to alert them about the flaws in the original demographic study and was also why I joined the district’s future enrollment committee last year along with several other community volunteers to work with demographer George Sundell directly to better understand the major drivers of the recent enrollment growth and to build a more robust enrollment forecast.

While the future enrollment committee made progress in areas such as forecast methodology, the committee was unable to complete its work and ceased its activities after the board hired M&M last fall to conduct a long-term planning review. At our last meeting, I spoke on behalf of the committee and clearly outlined to M&M’s lead consultant Mike Zuba the major issues that need to be addressed in their enrollment study. To my utter dismay, when M&M presented their “findings,” I noticed that none of these major issues, issues that the committee had largely reached consensus on, were addressed in M&M’s enrollment forecast. Instead, M&M’s enrollment model reverted back to the flawed methodology and doubled down on the dubious assumptions used in the initial enrollment study. As a result, the projected future enrollment growth has most likely been inflated. Continuing with the current set of enrollment projections will undoubtedly lead the community to wrong and costly decisions. I’m laying out the key issues here as to why M&M’s enrollment forecast is flawed. Since the board president declined my request to release M&M’s models in advance of the community forum, my analysis relies primarily on M&M’s presentation slides and publicly available data. As you will see, my numbers and argument are quite straightforward. You won’t need more than middle-school math to follow along.

To understand enrollment forecasts, it is important to introduce the cohort survival method, a simple statistical model widely used by demographers. The model uses historical student grade matriculation trends to predict future enrollment. The most important inputs of the model are survival rates, which are calculated by dividing the number of students of a particular grade level by the number of students of a grade lower in the prior year. In the case of “birth-to-K” survival rate, it is the number of kindergarteners divided by the number of births six years prior. Generally, higher survival rates lead to stronger forecasted enrollment growth and inputs of lower grade levels tend to have a disproportional impact on the results.

Inputs of survival rates are typically calculated using average survival rates of the past six years, a standard practice M&M acknowledges in its presentation (slide 24). However, in the three projection models presented – low, medium and high, M&M used five-year, weighted three-year and three-year average survival rates instead. You don’t have to be a demographer to question the wisdom of using a three-year trend to predict the future ten years out.

Overriding the standard six-year averages with higher and shorter-duration ones was one of the problems extensively discussed by the future enrollment committee. Committee members were concerned that the original demographer failed to sufficiently justify the use of three-year averages for the birth-to-K survival rates and managed to convince him to change them back to six-year averages. In my conversation with M&M consultant Rebecca Augur after their presentation, she couldn’t give a clear answer to why they chose to deviate from the standard practice. The effect of these overrides is difficult to assess without seeing the actual models and is further complicated by the fact that there are some sizable discrepancies between historical enrollment and birth data used by M&M and those used by the original demographer.

Flipping through M&M’s 94-page slide deck, you will be excused for not being able to pinpoint what exactly are the underlying drivers that will sustain the recent enrollment growth well into the next decade. The number of births has been on a decade-long declining trend. Housing transactions are cyclical and will always ebb and flow. Importantly, the underlying data seems at odds with the assertion that Princeton has been on a path of strong and sustained enrollment growth. According to PPS’ Comprehensive Annual Financial Report (CAFR), enrollment grew a total of 461 students in a ten-year period between 2009 and 2018. Yet, enrollment growth in 2015 (141) and 2017 (198) alone accounted for 74% of the overall growth. Does this astonishingly concentrated growth suggest sustained growth or anomaly instead? On slide 13 of the M&M presentation, we can see that the enrollment spikes in 2015 and 2017 coincided with the large number of tenants taking occupancy in the newly opened multi-family housing developments. Based on M&M’s numbers (slide 28), it is estimated that students generated by Avalon Princeton, Copperwood, Merwick and Stanworth since 2015 amounted close to half of the total enrollment increase of that ten-year period. Why does this matter?

First, lumping in enrollment originated from these multi-family housing units overstates survival rates and obfuscates the fact that “organic” enrollment growth driven by local demographics and housing transactions has been quite modest. M&M acknowledges this fact in its presentation (slide 28) by stating “There [multi-familiy] developments have contributed to elevated cohort survival rates over the last four years…” Second, since the students from the anticipated multi-family units to be constructed as a result of the affordable housing settlement are added on top of the projections of the cohort survival model, not excluding students from multi-family housing units while calculating historical survival rates inflates future enrollment growth by double-counting the effect of multi-family housing developments. Lastly, cohort survival method is not suited to forecast enrollment growth of multi-family housing units where the total number of housing units is fixed. With the occupancy rate at some of these developments already exceeding 90%, enrollment in multi-family developments cannot grow indefinitely. Not surprisingly, M&M’s enrollment forecast looks outlandish. For example, M&M’s medium-level model predicts that enrollment will grow by about 400 students in the next five years. Since the anticipated multi-family housing developments resulting from the recent affordable housing settlement agreement aren’t expected to produce meaningful number of new students until 2023 at the earliest, it seems highly unlikely enrollment for the next five years will grow at almost double the speed of the past ten years during which close to 900 multi-family units were created and occupied.

The school district leadership is fully aware of my long-held argument that a robust enrollment forecast requires modeling the “organic” growth and multi-family developments separately. It was clearly communicated with M&M as well. The previous demographer had agreed to run an alternative model using this method, although the Enrollment Committee didn’t get a chance to fully evaluate his preliminary results. So why did M&M knowingly choose to use the flawed methodology?

I can go on with more. But I guess you have got the gist of my argument. I didn’t write this letter to name and shame. I only did this because my many attempts to persuade the school district leadership in a more discrete manner have yielded nothing but frustration and disappointment. Public opinion seems to be the only thing that stands between our school district leadership and a problematic path they try to lead us down.

I again urge the school board to release M&M’s forecast models and key supporting documents so they can be thoroughly reviewed by the public. It is easy to pay lip service to transparency and making evidence-based decisions. It is only when the evidence contradicts our preconception that our honesty and integrity are truly put to the test. In a time when the school district leadership’s credibility is at a dismal low, taxpayers need to be convinced that consultants paid with taxpayer dollars are indeed working for us.

Mr. Chen works in finance and is a Princeton resident.


  1. Data can be tricky, but the enrollment study should be published given that it is the main rationale for the need to have another referendum.

  2. Mr. Chen, thank you for speaking up.

    Sadly, Princeton taxpayers ponyed up $144,000 to get reliable estimates, but ended up with a flawed analysis that, nontheless, supports the PPS board’s free-spending ways. Did Milone & MacBroom provide inept consultants who failed to catch an obvious anomaly in the data or able consultants who answered to a board whose goals are not aligned with Princeton taxpayers? Shouldn’t M&M address the findings of the Future Enrollment Committee, whether they agreed with the findings or not, or did the PPS Board fail to present them and give them the weight they deserved, wasting not only taxpayer money, but also committee members’ time? Did the PPS Board properly vet their consultant, adequately supervise and scrutinize their work, and bring the team up to speed on the insights entrusted to them by the Future Enrollment Committee or did the board simply use taxpayer money to buy a report tailored to support their preferred spendthrift course of action. Either way, it seems foolish to trust the current PPS Board with our tax dollars and our children’s future.

  3. Thank you, Mr. Chen! I’m very disappointed that PPS leadership chose to close down the work of the Future Enrollment Committee last September. These dedicated and locally knowledgeable residents, with various relevant skills, were doing their best to take into account the anomalies of the last five years’ enrollment, due primarily to the drivers introduced by the opening of Merwick-Stanworth and Avalon Bay. The Committee should have been allowed to complete its work. Instead a PPS “Strategic Committee on Growth and Capacity” stepped in and I believe made a presentation at a School Board meeting…..without conferring and discussing the complex issues of enrollment projections with the Future Enrollment Committee. This makes no sense at all. Then M&M was hired…. and here we are today. I think the original Future Enrollment Committee, all volunteers working for free, must be given an opportunity to sit down with the M&M people and see where they agree or disagree. Then the result of these discussions should be made public. This is what transparency is all about!

    1. Call me cynical but I honestly think that PPS BOE wheels are already in motion and these community events are just to be perceived as they plan to listen to what Princetonians have to say, just a show. It seems that they hired a company that is coming up with the numbers they want to justify another referendum. I am all for public education but not for fiscally irresponsible expenses. Another referendum? Seriously? And how many millions this time? Again 180? 150? 129? Or another 27? In my view, the credibility of the PPS BOE is gone.

  4. Thank you Jian for a thorough recap of the Enrollment Committee’s work and for clearly presenting the flaws in the recent enrollment predictions presented by M&M. As a fellow Future Enrollment Committee member, I am befuddled that community members were specifically asked by the PPS Board leadership to join the committee, provide input, review multiple enrollment studies, and participate in meetings only to have these efforts to go unconsidered by the recently hired planning consultants. I am more and more convinced there is a subset of the PPS Board intent on pushing forward a large scale capital project regardless of whether enrollment estimates support such a project or not.

    Taxpayers should know that the work completed by the Enrollment Committee leading up to the November 2019 meeting produced an analysis completed by Sundance Associates that predicted an enrollment increase of 278 students as of 2024 and only 11 additional students added through 2029 for a total of 289 new students over the next 10 years. My guess is these increases are too close for comfort for some Board members to the total number of out-of-district students attending PPS schools. While I would not propose turning away students currently enrolled in PPS, I do think it is worth considering what it would look like to end the arrangements over time to solve the over-crowding in our schools instead of Princeton taxpayers being force fed another pie-in-the-sky referendum.

  5. Wendy — Thanks for supplementing Jian’s article. I have forwarded both to M&M’s Project Manager, Rebecca Augur. We need to broaden the conversation publicly by including all responsible parties. While individual BoE members seem to be making progress it is strange indeed that there was essentially nothing in the Jan 25th event.

  6. While it is true that District officials are manipulating numbers to make their case, clearly Mr Chen is as well. Mr. Chen and his supporters would like to halt expansion of our schools. That is their goal. They seek to bog us down in an argument over mathematical models which of course is intended to confuse and delay.
    While the obvious current problem of overcrowding in our schools continues. There is no need to look to the near future. Our schools are now too full.
    So what should we do? Should we cross our fingers an hope recent growth is an anomaly? So the next generation of kids have a lower quality education. So what? This seems to be the thinking of Mr. Chen and his crew.
    Luckily, past residents were smarter and built enough schools 60+ years ago to get us to 2020. And now it is our turn.
    I understand that residents without young children and those in or close to retirement will be more concerned with money than with the future of our schools and future economy of Princeton. After all it is the high quality schools that attracts all the college educated workers who in turn attract all the companies that employ them. A continued slip in the quality of our schools will have direct and long term consequences.
    We should shoulder our responsibilities and stop quibbling over percentage points.
    The question we should be asking is if the district’s plan is long term enough and helps secure a healthy future in Princeton for the next 60+ years. After all, that is what our grandparents did.
    Thank you,
    Hal Friedlander
    PPS Parent

    1. All: I’ve just learned that there is a meeting on Feb. 14 from 2-3:30 in the Valley Road offices. I can’t find any mention of this on the PPS/BOE website (there are meetings listed for the 11th and 13th, but NOTHING for the 14th), but a “concerned parent” posted information about this to the Facebook post for Jian’s letter. The meeting was only announced on Friday in an e-mail to parents and staff, but has yet to be made public to the Princeton community as a whole. The details are as follows:

      “If you are interested in learning more about the factors, formulas and assumptions our demographers used to project that growth, I would like to invite you to attend a Demographics Discussion on Friday, February 14 from 2:00 – 3:30 at the Board Office, 25 Valley Road.

      The discussion will be facilitated electronically by Mike Zuba and Rebecca Augur, our consultants from Milone and MacBroom. We will also have present George Sundell, another demographer for the District, Ralph Widner, the former chair of our Future Enrollment Committee, and Bob Powell, the chair of our Strategic Advisory Committee and an expert in the school impact of affordable and related market rate housing.”

      This seems a rather important meeting to bury on the Friday afternoon before a long, holiday weekend. I’m sure many folks who work (like me) will be unable to attend given it takes place during the working day — and I suspect that many others will be getting ready to head out for the the 3-day weekend.

      However, I wanted to raise it here so that those who are concerned about the methodology, findings, and assumptions being used will be able to attend — to not only better understand M&M’s POV, but to also pose questions to ensure we’re applying evidence-based decision-making approaches to an issue that will have a long-term impact on our school district, our children and our community.

      Hopefully, in the interest of transparency, solid data and good will, Jian and other members of the future enrollment committee will be personally invited to attend given their knowledge of this subject and their work to date — and that this is will be the first of many discussions on this subject.

  7. @Hal New Jersey projects that there will be a significant decrease in the high school population statewide starting in about 5 years due to overall demographic trends. With that as a background, we should be concerned about spending a large amount of money for capacity that might not be needed except over the next 5 years.

    The errors that Mr. Chen cites appears to be real errors with the methodology of the report. No one is crossing their figures and hoping that the growth isn’t real. Instead, the data suggests that the growth isn’t really there. The burden of the proof should be on those who want to spend $100 million to show that we aren’t building unneeded capacity. That money could be used for other needs such as fighting climate change and poverty.

  8. Thank you for your comments, Hal.

    So I was right to say you don’t need more than middle-school math to spot problems in district’s enrollment forecast. It is quite obvious those numbers from M&M have been manipulated, isn’t it? For too long, our school district leadership seems to view public education as a zero-sum game between PPS families and non-PPS families. It is this kind of mindset that leads people down to the slippery slope of “the end justifies the means.” You and I might disagree on this. But I think defending public education is no longer a noble cause if that means we have to suspend our moral principles. That is especially true for leaders of our school district.

    I also don’t think your view is representative of the PPS families in general. Many PPS parents I know understand that their property taxes don’t even come close to cover the costs of their children’s education in our public school and they are grateful to their neighbors who pay taxes but don’t have children in our public schools. Few of them think building schools for the next sixty years is a prudent idea. Many folks who questioned the school board’s expansion plan are those who have quietly supported our schools for decades. Are they not entitled to know whether their hard-earned money will be spent wisely? It seems rather insensitive to tell them to “stop quibbling over percentage points.”

    I don’t have a crew. These are like-minded fellow residents – people who go to BoE meetings and ask probing questions. They might be a nuisance to some and they don’t get all things right all the time. But these are people who defend our democracy. More importantly, they are ones who believe their individual action can make a difference – a precious quality of the lovely people of this great country. I have nothing but respect for them.

  9. So let me get this straight. The school board disbanded a volunteer committee that was setup to estimate enrollment projections and instead hired an expensive consulting firm. Any consultant knows which side their bread is buttered on. This is straight out of Dilbert. They expect us to take these projections seriously? Can’t wait to vote the rest of them out.

  10. My main concern is that pretty much everyone taking a position on enrollment growth seems to be trying to find the One Correct Projection, based on the One True Model.

    As George E.P. Box observed long ago, “All models are wrong, but some are useful.”

    Prudent planning for the future must consider multiple projections, based on multiple models and multiple sets of assumptions, and include extra capacity to protect against the need predicted being wrong.

    My second concern is that nobody seems to be considering the train wreck in progress in all government finance, including schools, especially in New Jersey, as the inexorable growth in the cost of each government employee collides with the limited ability of taxpayers to pay taxes that grow faster than their incomes.

    I’d like to see some consideration of the possibility that buying some extra physical space would support experimentation with patterns of learning that rely more on students and less on teachers. The Administration of the Princeton Public Schools talks nebulously about “Innovation and Experimentation”, but only to try to improve learning, without much consideration of what the various improvements would cost.

    I’ve seen no consideration of possible tradeoffs between physical space and teacher count, other than ritual assertions that large class sizes are bad and the inference from that assertion that buying more physical space will inevitably cause the hiring of more teachers.

  11. @Rod Thanks for reminding people that the assertion that large class sizes are bad is unproved. If we can avoid the need for a large building referendum by having larger class sizes for the next five years, we may be able to use those savings to invest in teachers over the next 30 years.

    We need to be very careful about building for the sake of building as new facilities cost money to build and operate.

    1. Isn’t talking about “building for the sake of building” just setting up a strawman to knock down?

      I’m not suggesting that class sizes can be arbitrarily increased without changing the pattern of teaching and learning. I’m suggesting that larger spaces, properly equipped, can let students learn in ways different from the ways currently customary, with less teacher supervision.

      Just packing more and more students, like sardines, into spaces already too small for current enrollment, does not strike me as a wonderful idea.

  12. Agree re the larger class sizes. As a PPS parent I’ve made peace with them for pragmatic reasons e.g. larger forces like the demographic swell in empty-nesters who are very vocal and seem to be neutralizing the effect of new families and kids coming into the school system; like living in a University town that has many residential properties not counted towards rateables and grad students with kids in the system; like the Federal Govt putting ceiling on property tax deductions, and so on and so on.

    Also agree because a lot of current research I’ve read points to hiring more counselors as adding the most value to schools at this time. Which makes sense to me in the PPS context given the “know every student” philosophy and the wide range of educational needs our district serves.

    Also agree with Mr. Montgomery re the “One Correct Projection” focus, which is ridiculous. In the end, human beings still need to make decisions based on data and–in the best and at same time worst case–based on multiple sources of it.

    Everyone losing their minds over each line-item expense and over which projection to use is afraid of the control control we’ve given to decision-makers based on electing them (and the superintendent reports to those we elected). If you don’t agree with them, vote them out. I bet we’ll be in the same place after that unless one of the larger forces noted above shifts or something else major comes into play at the state or country or global levels over which PPS and the BOE have no real control.

  13. Simply enlarging class sizes won’t do it. What if PPS were to to rethink the whole operation? For instance, a single Montessori teacher may work with up to 40 children, but these children are taught how to work independently, and with and for each other (no bullying). Critically, the teacher has been taught how to “direct”, i.e., to see what’s needed and make it accessible, rather than telling a whole group what to learn next. If not all children do well in Montessori, consider the Dutch system, which includes Montessori and Waldorf options, and perhaps others, within the public system. I have met Dutch students attending such schools. Let’s acknowledge that there is no one way to learn. Can we try to move the system from one that’s curriculum- or subject-based to one that’s needs based, that encourages and develops independence from the get-go?

    1. Ms. Clurman inspired me to search the web for articles about space needs for Montessori schools.

      I found these:

      Looks to me like a Montessori school needs rather more physical space than a school based on classrooms stuffed wall-to-wall with one-size-fits-all desks, all facing the slightly bigger desk for the teacher at the front.

      Yeah, “stuffed wall-to-wall…” is a strawman too. I don’t think the Princeton Public Schools use all their space that way, though I suspect some spaces in the Princeton High School are used closer to that way than they should be. I also suspect that the State’s capacity-measurement rules assume something pretty close to it.

      I don’t think a district public school in New Jersey can go full-out Montessori: there are too many State constraints on how much teacher time must be applied to each student in each State-defined subject, with both students and teachers punished if students fail to score high enough on the State-mandated high-stakes tests administered on the rigid State-specified schedule.

      Nevertheless I think there’s room, within the State mandates, especially at the secondary-school level, for some Montessori-style student-organized and student-paced learning, under looser supervision by fewer teachers, if there’s enough physical space and equipment and materials for students to work that way.

  14. There will be a meeting on Feb. 14 regarding the PPS planning process and demographics, which is open to the community and will include Ralph Widner (who is mentioned in Mr. Chen’s letter). From a PPS email sent out late in the week:

    “If you are interested in learning more about the factors, formulas and assumptions our demographers used to project that growth, I would like to invite you to attend a Demographics Discussion on Friday, February 14 from 2:00 – 3:30 at the Board Office, 25 Valley Road.

    The discussion will be facilitated electronically by Mike Zuba and Rebecca Augur, our consultants from Milone and MacBroom. We will also have present George Sundell, another demographer for the District, Ralph Widner, the former chair of our Future Enrollment Committee, and Bob Powell, the chair of our Strategic Advisory Committee and an expert in the school impact of affordable and related market rate housing.”

    1. Lynda, thank you for sharing the presentation information. Unfortunately, this discussion is taking place on a day when PPS schools are closed and many, including myself, will be away for the long weekend.

    2. Will the meeting be filmed and the resources made available on the website? It’s scheduled during the workday and some of us aren’t able to attend.

  15. @Rod The problem is that people already seem committed to their positions. There are examples of classes that are at capacity in PPS and one can reasonably say that even modest enrollment growth will make the problem worse. There are also examples where teachers and classroom space are not being used as efficiently as they could be. More effective use could mitigate the need for new construction, or reduce the amount of new construction needed.

    In such an atmosphere, many attempts to find a middle ground are viewed suspiciously by either side. We are emblematic of the political divide in this country in our inability to work together.

    The building referendum has become a battle in which one side believes it is a fight for public education and the other side believes it is a fight to preserve Princeton as a place where the middle-class can live.

    I believe any building should be kept as minimal as possible as the long-term costs (building and operating) are substantial. I believe our students will benefit more by ensuring that this money is spent instead on maintaining our talented group of teachers. This is a choice we should be clear about as all funds come from the same place: the taxpayer.

  16. Rod — Thanks for the research. I’m aware that space needs differ. I suggest first only that independent study needs to be better understood and utilized; and then that cooperation with the private schools might be worth looking into further. Why compete, rather than cooperate, when it comes to education?

  17. Anonymous asked if the Friday meeting will be filmed and available. My understanding is that it will be live-streamed as well, but also that, in response to public concerns it will be moved to a later time and date. Last night’s meeting was dense with explanations and stats on budget. There is no policy in place to livestream such meetings (this was a “budget workshop”), so they are not routinely made available. It was noted in public comment period that it would be good policy to do so.

  18. And _now_ the District Calendar shows a Demographics Discussion at 7:00 PM to 8:30 PM on Thurs 13 Feb 2020.

  19. I would like to thank the School Board and Supt. Cochrane for listening to the community and moving the enrollment projection discussion with M&M to Thursday Feb 27, at 7 pm (at Valley Rd.) This will permit far more people to attend than the original date and time.

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