The Cosby Show: Season 2, Episode 13

2 - 13: Vanessa's Bad Grade

Vanessa, a straight A student, finds that her grades suffer when she studies with Robert, a classmate that she has a crush on. With a big school dance coming up, she is afraid to show her parents a bad test grade fearing they will keep her home. The night of the dance, Vanessa wears Denise's new sweater without her sister's permission, causing an all-out brawl between the two.