The polling stations were bombed using planted explosives device.
Earlier this month, two other schools serving as polling stations were bombed at the village of Chattar in Naseerabad district in Balochistan.
Violence has risen sharply before the vote with at least 61 people killed in direct attacks on politicians and political parties since April 11, according to an AFP tally.
Abdul Fateh Magsi, who was running for the regional assembly in Balochistan as an independent, was killed last month when his guards exchanged fire with tribal policemen at a check post outside the town of Jhal Magsi south of Quetta.
In much of Pakistan, a direct threat from the Taliban against the three parties in the outgoing government has curtailed public rallies before the polls, which will mark an historic democratic transition of power.
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