However, the fourth floor of the building where the Science laboratory is located will remain closed and off limits to students for the time being.
Councilor Jejomar Binay Jr. said experts have assured that it is now safe to hold classes at San Isidro National High School.
School officials are considering the possibility of moving the Science laboratory to another room where chemicals will be stored in sturdier shelves and cabinets.
Binay said experts have certified that according to tests, chemical residue in the school building is already below dangerous levels but authorities will continue monitor the air and the fourth floor.
Nine people, including six teachers, were hospitalized after chemical stored inside the science laboratory fell and crashed on the floor last Nov. 26.
Toxic fumes caused them dizziness, shortness of breath, and skin irritation prompting rescue teams to bring them to the Ospital ng Makati.
Residents living within a 100-meter radius were asked to leave their homes until it was safe to come near the campus again.