The settlement of Feriza and the boarding school were evacuated protectively, a fire brigade official said, adding that there were no reports of casualties or damage. About 30 children had been transferred to a nearby hotel.
At least 40 firefighters supported by 16 fire engines, two aircraft and four helicopters battled the blaze, which broke out around midday.
Traffic was diverted and TV images showed residents, wearing masks due to the coronavirus pandemic, standing in the streets nearby.
Greece often experiences wildfires during its dry summer months. Temperatures have remained high for the season, and authorities have warned of the high risk of blazes this week.
A forest fire was also burning near the seaside town of Nea Makri, north-east of Athens, the fire brigade said.
Early on Wednesday, fires broke out in a migrant camp on the island of Lesbos, destroying tents and containers and leaving thousands of people homeless.