There are seats for 93,000 students in the Boston Public School system but, according to some estimates, only 57,000 bodies to fill them. That deficit has led Mayor Marty Walsh and Superintendent Tommy Chang to signal, cautiously, that they are prepared to look at closing some public schools to free up money in the budget.

Former Massachusetts Secretary of Education Paul Reville says that's a controversial step, but an essential one.

"I've got to commend the mayor and the superintendent for bringing this forward, because there are savings. There is no question that there are savings," said Reville.

"The fact is, as enrollment is going down, you need fewer facilities and you should need fewer teachers in order to do that job, and you have to come to grips with that," he continued.

Reville said school closings can be political minefields, especially when those closings appear arbitrary or disproportionately affect low-income or minority students. 

"Where it gets into problems is if it seems arbitrary: who is on the list and who is not on the list, and if the list—when it is announced—is subject to political influence. In other words, some get removed from the list, some get added, that's what typically creates a furor," he said.

But there is a smarter way, Reville continued. Some districts have created independent, impartial closing panels or formulas to evaluate a school based on the quality of the school, the neighborhood in which it is located, its academic performance, and other factors. Then they produce a list of proposed closings and submit it to a body like the school committee or the mayor for an up-or-down vote. No schools can be added or subtracted from that list to insulate it from outside political pressures.

"You can't tinker with it," Reville said.

Paul Reville is a professor at Harvard University's Graduate School of Education where he also runs the Education Lab. To hear more from Reville, tune in to Boston Public Radio above.