The remote-controlled bomb was planted at the outer wall of the government-run middle school in the outskirts of Mardan town.
The bomb exploded after police arrived to investigate complaints about a suspicious plastic bag outside the school, which was closed at the time.
According to police sources, one policeman was killed and eight other people including five civilians were wounded. Three policemen were also wounded but no pupils were hurt.
Police said the terrorists targeted the school.
