Date Bait (1960) on Netflix

Plot summary

Sue Randall and Danny Logan are in love, but her father considers Danny beneath the family. At Pancho's, the teenage hangout, Brad Martinelli, newly home from drug rehabilitation, confronts them, jealous that Sue prefers Danny to him. Brad pulls a knife on Danny, and his older brother Nico, a mob-connected drug dealer, calms him and promises to handle Danny. Nico and his henchman chase Danny, beat him, and warn him to stay away from Brad. When Mr. Randall sees the bruises, he orders Danny away. Danny's attempt to speak with Mr. Randall at his office fails when Danny mentions that he and Sue would both work. Sue proposes they marry right away to prove their seriousness, and they plan to elope to Las Vegas that night, lying about their ages.