Three students and one teacher were left dead in the incident in the province of Kahramanmaras, Governor Mukerrem Unluer told reporters.
The student was in the eighth-grade at the school and concealed their father's guns in a backpack to carry out the attack, the governor added.
School shootings are very rare in Turkey.
Television footage from the scene on Wednesday showed ambulances arriving at the school where police and crowds had gathered by the gate. Justice Minister Akin Gurlek said on X that an investigation was launched into the attack, Reuters reported.
On Tuesday, a former student opened fire at a school in the southeastern province of Sanliurfa, wounding at least 16 people, including students and teachers, before killing himself.