The Delinquents (1957)

Scotty White (age 19) must stop 'going steady' with Janice Wilson (age 16) when Janice's parents intervene. Frustrated, idle and without Janice's restraining influence, Scotty encounters Cholly and his band of disorganized, fun-loving delinquents. Soon he has Janice (who seems considerably the more mature of the two) mixed up in their doings, which begin to seem less and less like harmless fun...