The Carlisle Mosquito Online

Friday, April 14, 2000


How fast will Carlisle School grow? More confusion than clarity

The Carlisle School expansion subcommittee should find a qualified demographer to do a careful and professional study of enrollment trends before doing an engineering feasibility study of the Banta-Davis Land, selectman John Ballantine urged at their March 9 meeting. Several weeks after the meeting, the school committee formally requested that the selectmen add to the Warrant an article authorizing $15,000 for the feasibility study alone.

Ballantine, a Brandeis economist, has himself been trying to estimate increases in the total number of children at the Carlisle School over the next five years or so. He is a co-author of "Growing Pains," a Carlisle study released last spring, reporting on the costs to the town to provide services for households in newly constructed and recently purchased homes. For this report, the authors used information from the annual town census and school records to estimate how trends among families moving into and out of town increased enrollment at the elementary and high schools from 1994 to 1998.

For the ""Growing Pains" effort, Ballantine employed a technique commonly used by school systems, including Concord-Carlisle High School, to predict future enrollment. This analysis started with the number of preschool children reported in the town census and the number of children enrolled in the public school (excluding children in private schools) in 1998.

Next, to project the total size of each school grade or age group (referred to as a "cohort") the following year (1999), the average net increase from "move-ins" and "move-outs" for each age group was calculated, then added to the current numbers. The total numbers in each cohort then provides an estimate of the town's elementary school enrollment and the preschool population for the next year. For subsequent years, the analysis can be repeated using the projected numbers plus average net increases.

This procedure was the basis for Ballantine's predictions of Carlisle Public School enrollment for the next four to years, which Ballantine noted can only provide relatively accurate projections for some "few" years.

New predictions for 2000-2005

Ballantine has revised his predictions for 2001 to 2005 based on this fall's school enrollment and updated preschool numbers from more recent town census reporting by Beth Hambleton, a coauthor of "Growing Pains" and member of the school building committee. At their March 9 meeting, Ballantine presented the committee with estimates showing last fall's total school enrollment of 774 rising to about 800 next year (2001), then remaining stable till at least 2005. The rapid growth the school has seen recently should slow when the two large classes, currently fourth and seventh grades graduate, if incoming kindergarten classes return to the levels of between 60 and 80 that were the norm up to a year ago, he said.

However, committee members were skeptical of Ballantine's estimates, which they fear are too low. They point to a kindergarten of 97 last fall (sharply up from an average of 72 between 1994 and 1998), and an equally high pre-registration for next fall, as cause for concern that the school may exceed its capacity of 900 students within a few years. School officials report that, as of April 11, 94 children are pre-registered for kindergarten.

Problems with kindergarten numbers

Several years of kindergartens larger than 90 children could mean the capacity of 900 would be reached within six or seven years, Ballantine noted. Based on past growth, each entering class will grow by about 20 students by eighth grade, so a kindergarten of 90 will swell to about 110 at graduation. In that case, the average grade at the Carlisle School would be 100, or a total enrollment of 900 for K through 8.

However, Ballantine acknowledged that this year there was a difference of seven between the projections based on the town census and the actual number enrolling in kindergarten. The size of the entering kindergarten class is much harder to pinpoint than the growth of the population once children enroll in school, where we have better records, he explained. That is, the "Growing Pains data shows that, on the average, move-ins and move-outs should produce a net increase of about 22 children a year in grades 1 through 8, mostly in the lower grades.

However, two factorsa possible under-reporting of preschool children in the town census and an uneven "flow" of 4- and 5-year-olds into school the following yearhamper accurate predictions of kindergarten size. In an interview following the meeting, Ballantine outlined the problems inherent in understanding this "flow."

Of the known five-year-olds in Carlisle at the beginning of the school year, some may enroll in the Carlisle preschool, some in private preschool, some in private elementary school. Some five-year-olds' birthdays may fall after the September 1 cut-off date, making them ineligible. In addition, some families with 5-year-olds will move out of town, to be replaced by an equal or greater number of 5-year-olds moving into town.

Undercounting of preschoolers?

Further complicating prediction, some five-year-olds who enroll may not have been reported to the town census at all. Town officials realize that there are undoubtedly preschool children living in Carlisle not counted by the town census, but how many is unknown. Town officials know there are lags in reporting that make it impossible to know precisely how many children of a certain age are living in town. The census is collected each winter, with compilation not completed until a month or so later, so a child who moves into town after February would not appear in the town census count at minimum until March or April of the following year. Moreover, new residents may not respond to the census the first year of their residency and some families do not list children on the census forms or do not list birthdates.

Ballantine showed the committee a chart of the yearly town census counts of children aged one to four over the past five years. The number in each age group and the total increased substantially in 1995, but remained fairly stable in 1996, 1997, 1998, declined in 1999, and thus far, in 2000, seems to have returned to the 1995 levels. In the later interview, Ballantine observed that, since these figures don't show any increase in the last three years in reported preschool children, the high kindergarten enrollment this year (and expected for next year) "do not make sense unless we have some serious undercounting" on the town census.

This year's surge an anomaly?

Next year's expected kindergarten class (currently reported at 94) is also more than Ballantine's estimate of 91, but "we don't know why," he worried. Although new construction and existing home sales have been brisk, that has been true for much longer than the past two years.

Ballantine expressed concern to the committee that this (and possibly next) year's growth could be an "aberration," rather than the initial wave of a dramatic expansion of the school population. Nonetheless, based on a closer analysis, he has revised his predictions since March 9, adding 13 to the number of children projected to enter kindergarten in each of the next five years. These newer estimates show the total school population rising to 813 in two years, then a bit more sharply to 868 in 2005, which is still within the present campus's maximum capacity of 900.

After 2005, assuming no comprehensive permit subdivisions or major demographic changes, enrollment could "easily stabilize" between 880 and 930 or even decline, as the large classes now entering move on to the high school, Ballantine believes.

Another approach to the numbers

At the March 9 meeting, Ballantine also referred to the conclusions of Lenny Johnson, chair of the town's long-term capital requirements committee and a former finance committee chair. Johnson has explored potential future school enrollment trends from a different angle, by studying the dynamics of change in the make-up of Carlisle's adult population.

Key to predicting trends in the number of K-8 children living in town are the ages of female residents, Johnson said. From the town census he has learned that nearly all mothers of elementary school children are between 35 and 50 years old, so changes in their number augur changes in the K-8 population. That is, when the number of women 35-50 (in 1999, just a little less than half the households in Carlisle) stays about the same, over time elementary school enrollment should stabilize; if the number of women that age declines, then enrollment would eventually drop, and vice-versa.

Since everyoneschool children and their parentsgets older every year, if there were no new construction or resales of existing homes, eventually all Carlisle residents would be retirees and the school population would then surely decline, Johnson observes. However, resales of existing homes along with new construction bring new members of the 35 to 50 age cohort into the community, as current parents age and leave the school.

Thus, whether and when enrollment will outgrow the capacity of the current campus depends in large part on how many residents stay in town after their children finish eighth grade and do not sell their homes (because only residents who leave are replaced by families with school-aged children).

What will over-50 households do?

Johnson's analysis shows a large group of nearly 300 female residents aged 45 to 49 in 1999, the leading edge of the baby boomers. Of that group, 50 to 60 of those households per year will join the ranks of "empty nesters" or parents of adolescents among townspeople. Whether and for how long those people remain in their homes after the children have left school will help to determine the size of the school in 2005 and 2010, he believes.

What they will do is "the big unknown," Johnson said, and there has not been as much notice or investigation of what has happened historically with this age group as for families with children. If more stay in town than move, the size of the school could stabilize, or even decline, for a while.

Thus, though surprised and concerned, both Ballantine and Johnson are hopeful that the abnormally high projections for next year's entering class are not a sure sign that the school will outgrow its capacity immediately. Ballantine believes that the K-8 school population could reach 820 to 850 by 2005, and that a peak of 900 to 1,000 will occur in the 2010-2015 time frame, then "tail off...toward the 850 level" as fewer new homes are built.

Johnson has also explored demographic projections for Carlisle in 2010, based on 1990 Federal census figures (since the 2000 Federal census results will not be available until next spring). The Massachusetts Institute for Social and Economic Research (MISER) at UMass projects a total of 950 children aged 5 to 14 would be living in town in 2005, falling to 920 in 2010. Allowing for at least 100 of these children being enrolled at CCHS or in private school, at that level CPS enrollment in both 2005 and 2010 would be below the 900-student maximum capacity.

Copies of "Growing Pains" are available at the Gleason Public Library.

Nancy Pierce is the FinCom reporter and co-author of "Growing Pains."

2000 The Carlisle Mosquito