A second demographer has confirmed for the school district that the elementary population is expected to decline for several more years and remain relatively low for some time after that.
“We both use the same underlying methodology,” Peter Prowda told the school board Monday, presenting his enrollment figures.
The projections are used for planning staffing needs from year to year, but they’ve taken on greater long-term importance as the district plans to close one of the district’s six elementary schools when the student population dips below 2,000 and is projected to stay below that figure for at least a decade.
Dr. Prowda’s projections closely resembled the figures presented by the district’s regular demographer Hyung Chung.
While Dr. Chung provides three sets of projections — “high,” “medium” and “low” — Dr. Prowda offers only one.
For the first five years of Dr. Chung’s report, when birth rates for future kindergarten classes are still known, his high, medium and low projections are the same.
Dr. Chung projects K-5 enrollment to drop below the 2,000 mark in 2015-16, while Dr. Prowda projects that to happen in 2016-17.
Dr. Prowda explained his methodology in broad strokes.
Like Dr. Chung, Dr. Prowda builds his data on birth rates from five years prior to the school year in question.
In affluent communities like Ridgefield, Dr. Prowda said, “a lot of parents hold their kids out who are October, November, December babies,” so he accounts for those students as well.
Then he multiplies the birth rates by a “birth to kindergarten growth” rate based on the past five years.
“The recent past is a good predictor for the future,” he said.
A chart of birth to kindergarten growth rates from 1997 to 2007 showed the number of children born in Ridgefield five years earlier and the number of students enrolled in kindergartner in a given year ranged from 103% to 134%.
He similarly builds a grade-to-grade growth rate based on historical data as well, so he can estimate how class sizes will change as one group of students moves through the school system.
Dr. Prowda said that, if anything, his estimations err on the high side.
He said he thinks long-term birth estimates in towns like Ridgefield are skewed too low in state planning data, in part because a large portion of the ‘childbearing age’ population, which is important for long-term population estimates, vanishes from town soon after adolescence.
“As you guys know, you lose a lot of people in the 20 to 25 year old group — they’re off to college,” Dr. Prowda said.