Dozens of students at Swift Middle School in Watertown were hospitalized Thursday after an odor filled the building on Thursday morning.
One child passed out and dozens more complained of nausea and being light-headed, according to the superintendent.
The school, located at 259 Colonial Street, was evacuated just before noon when the students began to feel sick.
The affected students were not concentrated in one area of the building, but were located throughout the school, the superintendent said.
In all, 24 students who were sickened were taken to Waterbury Hospital and another 19 were sent to Saint Mary's Hospital. All students have been treated and released.
The school dismissed early around 12:30 p.m.