Some Kind of Wonderful (1987)

Keith Nelson, an artsy high school outcast, tries to land a date with popular girl Amanda Jones with some help from his tomboy best friend, Watts. However, Watts realizes she likes Keith as more than just a friend and tries to convince him to stop pursuing Amanda. Matters are further complicated when Keith's invitation draws the ire of Amanda's rich yet snobby ex-boyfriend, Hardy Jenns, who makes plans to get even.