If your school building was built or last renovated before 1980 and has not had a complete lighting upgrade since that time, PCB-containing lights are likely to be present. The use of older mangnetic ballasts or T12 lamps increases this possibility.
The only way to verify is to do a visual inspection of the lighting in your school. Use the Environmental Protection Agency's guide to identifying PCB-containing lights.
The ballast is a rectangular box in a light fixture that regulates the flow of electicity.
PCB-containing magnetic ballasts were commonly used in fluorescent light fixtures that hold T12 bulbs. The T means tubular lamps, and 12 indicates a 12/8" diameter. If you have these lamps in your school building(s), you could have ballasts that contain PCBs.