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nrollment in Massachusetts public schools has fallen nearly 4 percent — or by roughly 37,000 students — since fall 2019, a decline educators attribute to shifting demographics, housing costs, and fallout from the pandemic.

Some of the greatest declines have occurred in Greater Boston, where school systems in Marblehead, Rockport, Wellesley, Wilmington, Brookline, and Amesbury saw enrollments drop more than 10 percent, according to state data.

High housing costs driving out young families, aging suburbs with fewer children, and uncertainty among parents about the return to in-person learning during the pandemic could have long-term impacts for school districts as they plan budgets for students and staff, while communities continue to recover from the health crisis’s fallout.

“Our hypothesis is that, certainly, the pandemic exacerbated the decline’’ in enrollment, said Mary Bourque, the director of government relations for the Massachusetts Association of School Superintendents.

The Globe analyzed enrollment data collected by the Department of Elementary and Secondary Education for the school years of 2019-2020, 2020-2021, and 2021-2022. The data, reported as of Oct. 1 each academic year, is collected for about 400 districts, including local and regional schools, vocational schools, and charter schools.

Statewide, 911,529 students were enrolled in public schools in 2021-2022, compared with 948,828 in 2019-2020.

Nearly three-quarters of school districts reported enrollment declines during the three-year period.

Wilmington was among the region’s districts with the largest decline in students, state data show. Its enrollment fell 11.5 percent, from 3,166 students in 2019-2020 to 2,801 students in 2021-2022.

Glenn Brand, Wilmington’s superintendent, said there is no question the pandemic exacerbated what was an already anticipated decrease in students due to factors such as an aging population with fewer children.

More than half of the students who left Wilmington’s public schools during the pandemic opted for vocational school, private schools, or to be taught at home, according to Brand.

“There is certainly a belief that many challenges that public education faced through the pandemic ... seems to be at the root of some of those decisions of some of our families,’’ Brand said. “We can no longer assume that we are the only choice, because we are not.’’

The district has had to reduce one position at the middle school level, and another at the high school, in the coming school year because of the enrollment decline. But officials are trying to avoid increasing class sizes or cutting programs, which Brand said would be counterproductive.

In Brookline, the public schools’ headcount dropped by 849 students during the pandemic, a total behind only Boston, Worcester, and Springfield, according to state data.

Brookline’s enrollment fell 10.9 percent to 6,928 this past school year, from 7,777 before the pandemic began.

Superintendent Linus J. Guillory Jr. said the most precipitous drop in students occurred between March 2020 and September 2020. But the district is now seeing a return of many students: By June 1, the headcount had grown to more than 7,000, and officials are projecting between 7,100 to 7,250 students this upcoming year.

The pandemic’s biggest impact on Brookline’s enrollment came from health measures that closed international borders, as many families returned to their home countries, Guillory said. Now many of those families are returning.

Many local families who sent their children to private schools also are coming back, he said.

“I’ve had personal conversations with some families that have indicated that they left because of not knowing about the openness’’ of buildings, Guillory said. “But now that we’ve gone through a year [of in-person learning], they’re looking forward to returning back to us.’’

The Brookline school district has had to reduce staffing because of the lowered headcount, and has eliminated about two dozen full-time equivalent positions this past fiscal year, he said. The schools are entering the new year with a $3 million budget deficit, and there are discussions about a property tax override to help close the gap.

“Yes, this is definitely top of mind for us, and its impact on our organizations,’’ Guillory said.

In Rockport, climbing housing costs and an overall decline in school-age children are seen as the cause of the town’s drop in students, according to Superintendent Rob Liebow. Enrollment fell 11.8 percent, from 851 students in 2019-2020 to 748 this past school year.

The housing issues also are impacting where staff live, he said.

“There are a number of teachers who live in Rockport, but not as many as what you would expect to see. They’re commuting from Danvers and Beverly and Gloucester,’’ Liebow said in an interview.

Even before the health crisis, enrollment in Massachusetts public schools was declining, said Bourque, a former superintendent of Chelsea’s public schools. Once the pandemic struck in spring 2020, several factors might have accelerated the trend, Bourque said.

Those factors could include a real estate boom that caused many families to relocate; parents who opted to place their children in private school, or teach them at home; and a decline in immigration.

Officials are still studying the decline, she said, and it is unclear how the trend will unfold going forward.

The issue is important for school districts, which rely on enrollment figures to build their annual operating budgets.

Public schools are funded with a mix of local and state funds to provide staffing, materials, programming, and other services. Some of this funding is tied directly to the number of students in the district.

School officials are concerned that long-term reductions in enrollment will cause budgets to shrink — and force cuts to staff or changes in educational programming that could impact students.

“People are always looking at their budget, and having to adjust to the student need,’’ Bourque said. “And if the student need is not there, then the various adaptations have to happen in the budget.’’

In Greater Boston, a half-dozen school districts reported enrollment declines of 10 percent or more between 2019-2020 and 2021-2022, including Rockport, Wilmington, and Brookline.

Enrollment fell 12.2 percent in Marblehead (from 2,963 students to 2,601); 11.8 percent in Wellesley (from 4,862 students to 4,290); and 10.7 percent in Amesbury (from 2,012 students to 1,797).

Even as most public school districts in Massachusetts experienced enrollment declines, about a quarter reported increases during the three-year period, according to state data.

The majority that grew were either charter schools or regional vocational school districts. That group included the Essex North Shore Agricultural & Technical School in Danvers, where enrollment rose 10.9 percent, from 1,492 in 2019-2020 to 1,654 in 2021-2022.

Meanwhile, in the growing town of Hopkinton, the local public schools added 144 students during the pandemic years, an increase of 3.7 percent.

The district had 4,006 students this past school year, up from 3,862 in 2019-2020. School officials anticipate that figure will climb to about 5,000 by the end of the decade, according to Superintendent Carol Cavanaugh.

There has been a lot of construction in town, including Legacy Farms, a housing development on property once owned by Weston Nurseries. The development has brought new families with children, who now attend the public schools.

The complex will feature a total of 1,120 units, including 865 condos, 240 apartments, and 15 single-family homes, according to Norman Khumalo, Hopkinton’s town manager. He said 84 percent of the project’s building permits have been issued.

Hopkinton is a draw for families because it has a high-performing school district, Cavanaugh said, and the town has easy access to major highways, including Interstate 495.

The district also made early progress in vaccinating students and staff against COVID-19. In October 2021, Hopkinton High School became the first school in Massachusetts to get state approval to lift its mask mandate for vaccinated students and staff. At that point, at least 80 percent of that group had been vaccinated, according to the state.

In the past few years, Hopkinton opened the Marathon Elementary School, which serves about 560 students in kindergarten and Grade 1. Officials are considering whether to build another school to help with the growing student population, Cavanaugh said. Meanwhile, the town has approved larger school budgets to help keep up with the growing student population.

“The community is super supportive of the public schools,’’ she said.

John Hilliard can be reached at john.hilliard@globe.com.