BRUNSWICK — The number of students who have left Brunswick public schools for charter schools has nearly doubled since last year, placing a growing financial burden on the School Department, Superintendent Paul Perzanoski said Wednesday.

Perzanoski told the School Board 47 Brunswick students were attending three of the state’s charter schools, up from 24 last year.

School officials expect the number to grow at the same pace over the next few years, as charter schools add more grades and grow in size.

The majority of the students are attending nearby Harpswell Coastal Academy. Others are attending Baxter Academy in Portland or going to school online via the new Maine Connections Academy virtual school.

Seven of those students were either home-schooled or attended a private institution before moving to a charter, and almost all have been identified as special needs students, Perzanoski said.

That means Brunswick is starting to pay for students who may have never attended a Brunswick school, and never received any state aid for them, he told the board.

Under Maine law, local school districts are obligated to pay tuition for students from their jurisdiction who choose to attend schools outside the district. Any state financial aid also follows the student to the school of their choice.

At roughly $10,000 per student, Perzanoski said after the meeting, the cost to the district for charter schools is approaching half a million dollars annually.

About half of that, or $240,000, is additional cost to the district, which is not being balanced by reimbursement from the state, he added.

“We will never get the amount we spend, ever,” Perzanoski said.

School districts that are in close proximity to charter schools are being disproportionately impacted because it is easier, in terms of transportation, for parents to send their children to the charters, Perzanoski said.

But School Board Member Corinne Perreault suggested Brunswick previously benefited from the decisions made by these families, whose children were not enrolled in Brunswick schools, while their parents still supported the School Department as taxpayers.

“Not that I’m thrilled about the situation, but their families have paid taxes in Brunswick for years and haven’t used the services,” Perreault said. “So in one way, they have been paying towards the school department.”

Board Member Brenda Clough said the appearance of new students still created unpredictability for the School Department’s budgeting.

So far, the department has been able to gauge the number of students who might enter a charter school and budget appropriately, according to Perzanoski.

The best chance the district has to avoid ballooning costs is to support legislation that would distribute payment for charters across the state, he told the board. A similar bill failed during the last legislative session.

“Students and families need the opportunity to be involved in the choice of their education, but the financing of that education needs to be fair and equitable,” Perzanoski said.

An advisory panel tasked with designing new academic programing in Brunswick schools was recently established, partially as a way to remain competitive with charters, Perzanoski added.

“Public education can’t just do the same thing over and over again and sustain itself,” he said.

Peter L. McGuire can be reached at 781-3661 ext. 100 or pmcguire@theforecaster.net. Follow him on Twitter @mcguiremidcoast.