GROTON -- Groton-Dunstable Regional School Committee chose to enter "uncharted territory" April 24 when it voted to approve an expansion of the district's school-choice program.

With the vote, the School Committee gave the administration the go-ahead to add eight new school-choice students at Swallow Union Elementary School in 2013, eight for Florence Roche Elementary School, 10 for the middle school, and four for the high school.

Voting also included authorization for the administration to study the possibility of allowing out-of-state students to attend Groton-Dunstable as well, with the idea of charging them tuition for the privilege.

Committee members had been briefed on school choice at an earlier meeting when they were told of the possibility of filling empty seats with out-of-district students.

The question was prompted by the administration's concern over falling enrollment, which also meant falling revenue for the district.

According to the briefing conducted by Swallow Union Elementary School Principal Peter Myerson, the school district currently has 37 out-of-district students spread across all of its schools but mostly concentrated in the high school.

At the same time, Myerson reported that overall enrollment of in-district students continues to fall, with the school system having lost 10 percent of its student body since 2007, an assertion he repeated at the April 24 meeting.

Committee members were reminded that for each school-choice student the district accepts, it earns $5,000.

But the question of out-of-state students was one that needed further study, including questions of criteria for admission, dismissal, enrollment, and whether they would need to qualify for MCAS as Massachusetts students do. Not least among the issues to be reviewed was how much tuition to charge them.

"This is uncharted territory," said Myerson of school-choice expansion in general and out-of-state students in particular.

But when asked if enough choice students could be found to fill all the seats that would be opening up in the coming years, interim superintendent Anthony Bent said that would be no problem.

"They're breaking down our doors," said Bent of applicants. "I have little doubt that we'll be able to fill these seats next year."

Committee member John Giger, admitting interest in the expansion, nevertheless had concerns about applicants all having an equal shot at being accepted.

Bent assured him that except for first priority given to siblings of current choice students, a "strict lottery" would be used to choose finalists.

Committee member Jon Sjoberg expressed worry that the district might become committed with too many choice students, throwing off class sizes down the road.

"We have very low exposure," said Bent.

Bent insisted that class sizes at Groton-Dunstable are "really small," much smaller than many other districts in the state. With enrollment continuing to shrink, there is little danger of getting caught short.

In the end, the School Committee voted to approve the expansion with the intention of having the new influx of out-of-state students take place at the start of the 2014 school year.