Geo TV said a short circuit in a mobile tower inside the school, located in the Nothia area of Peshawar, caused the fire.
The blaze engulfed classrooms of the school, Geo TV reported.
Rescue teams responded to the site and 13 children were sent to hospitals for treatment of their burns, Geo TV said.
'Happy' fan videos make Pharrell cry [VIDEO]
Pistorius testifies he didn't consciously pull trigger when he shot girlfriend