Family Ties - Season 5 Episode 25 : "D" is for Date 1989

Jennifer develops her first major crush on science lab partner Tim Higgins, the handsome star pitcher of the school baseball team. When Tim comes over to work on their science project, Jennifer is thrilled, but also embarrassed by his open admiration of her academic talents. Believing the adage that boys never like girls who are smarter than they are, she decided the way to keep Tim interested is to play dumb.