The experiment was being conducted Tuesday outside the Yellow School in Bunker Hill Village. The school is located inside Memorial Drive Presbyterian Church.
Memorial Hermann Hospital spokeswoman Rhiannon Collette says the children are in good condition.
Village Fire Chief David Foster says several other children were released to their parents who are taking them to their own doctors for possible care.
Houston Fire Department Senior Capt. Ruy Lozano says an emergency medical team was sent to the school after children got chemicals on them.