WHEELOCK, Vt. — For more than a century Dartmouth College has been making good on a promise to students from a hardscrabble Vermont town that helped the keep the school afloat in its early years: get in, and your tuition is free. But in that time only nine students from the town of Wheelock have taken advantage of the offer of a tuition-free Ivy League education for those hailing from this community in the heart of Vermont’s Northeast Kingdom. Noah Manning, a 20-year-old starting his third year at Dartmouth, is the fourth Wheelock student to take the scholarship in the last half-century. “I had always heard about it,” said Manning.