The incident happened at José de Diego Community Academy on North Claremont Avenue in West Town.
At least seven children were taken from the school to hospitals in good condition, sources said. They were involved in a science experiment.
Chopper 7 was over the scene, where there appeared to be a hazmat response at the school.
ABC7 has reached out to Chicago Public Schools for more information.
This is a developing story. Check back for updates.