Besides classroom disruption, a fire started in the boys bathroom at Marana High School last week, caused minimal damage.
Tamara Crawley, spokeswoman for the Marana School District, said the incident occurred in the late morning hours of April 25.
While the incident is under investigation, officials believe students set a soap dispenser on fire.
A staff member noticed the smoke and took the necessary action.
Students were evacuated, and Crawley estimated they lost about 15 to 20 minutes of class time.
The Avra Valley Fire Department responded, clearing the scene quickly.
Crawley said while there could have been more damage, the department and staff acted quickly.
With no injuries, Crawley said it could have been worse and the incident is being taken very seriously.
Officials will investigate, and those responsible will be punished.
Crawley did not know yet how much the damage will cost the school to repair, noting that it is mostly smoke damage along one wall.