Summer vacation has ended, but temperatures in the 70s and 80s are likely in Boston through September. For the majority of the 56,000 students in the city's 124 public schools, returning to classrooms offers little respite from heat and humidity. Only about a quarter of the schools have air conditioning.

Unsurprisingly, newer schools are more likely to have AC. The 33 air-conditioned ones have almost all been built since 1970, with some undergoing renovations in more recent years.

The air-conditioned schools span the city, from Mattapan to the South End. Only one of Boston’s exam schools, the John D. O'Bryant School of Mathematics and Science, has air conditioning. Neither Boston Latin School nor Boston Latin Academy does.

This map shows Boston Public Schools with AC. Data from Boston Public Schools. (Molly Boigon/WGBH News)

Research shows a hot classroom doesn’t just make students and staff uncomfortable. Heat can also impact academic performance.

A 2018 studyfrom Harvard’s Kennedy School of Government found consistent heat exposure negatively impacts learning and productivity. The study also concluded school air conditioning “almost entirely offsets these effects.”

The Boston Public Schools said in a statement to WGBH News that the city makes special accommodations for students on hot days.

“BPS and the city currently work together to supply additional fans and water in school,” the statement said. “Additionally, BPS and the city carefully monitor weather conditions to ensure the safety of all students and staff."

The statement also said Boston is committed to modernizing school buildings and adding climate control as a part of a long-term master plan, BuildBPS.