Images from the scene showed students fleeing and some jumping from windows as police units secured the area.
The attack began around 09:30 local time, with the gunman using a shotgun to fire indiscriminately on campus. At least 16 people were wounded, including 10 students, four teachers, a cafeteria worker and a police officer. The attacker later took his own life as security forces surrounded the building, officials said.
Emergency services evacuated the school and transported victims to hospitals in Siverek, while several seriously injured were transferred to facilities in Şanlıurfa.
Governor Hasan Şildak confirmed a comprehensive investigation had been launched.
The incident has renewed concern over school safety in Turkey, where such attacks remain rare but have drawn increased scrutiny from authorities and educators.