The Big Bet (1985)

A teenage boy that had early sexual encounters is having trouble finding them now, and spends a lot of time fantasizing about the women he knows. When a beautiful new girl comes to town, he makes a bet with the other guys that he can get her into bed within 10 days. His chief rival stacks the deck, though, by threatening to expose the new girl's sordid past (she was wrongly accused of being involved in an orgy at her previous school) if she sleeps with our hero. Confused about his situation, the boy seeks counsel from the sexy older woman across the street, and she helps him come to terms with his predicament.