Town Meeting voters gave the $63 million middle-senior high school proposal the necessary two-thirds support on Monday, with 712 in favor and 209 opposed. The tougher hurdle will be the ballot vote on the project slated for Saturday. Polls will be open from 9 a.m. to 8 p.m. If passed, the school will be paid for with a 30-year tax increase, known as a debt exclusion, which would raise the annual bill on an average property of $288,000 by $648. The state School Building Authority has agreed to reimburse the town for $29.3 million of the project’s cost.