Less than a month after rejecting a proposed $8 million debt exclusion to build a new public works facility, Whitman voters will return to the polls to consider a permanent tax increase to pay for education. On Saturday, a special election will be held on a proposed $440,160 Proposition 2½ override to help cover the town’s share of next year’s budget for the Whitman-Hanson Regional School District. If passed, the tax bill on an average property would increase by $88.68 annually. Polls will be open on voting day from 9 a.m. to 5 p.m.