Tom is in highschool, not college

Tom Lee attends Chilton Academy, a boarding school for boys of highschool age.
It is what is called a "prep school", or a school that prepares the students for colleges, presumably the ones like Harvard or Yale.

The name Chilton Academy is on the side of the bus that arrives at the beach to take the boys back to the school.

Tom is seventeen through most of the film. The story appears to be set in the spring. In the first scene with Laura, she is in her garden where the daffodils
she planted in the fall are blooming. He turned eighteen near the end of the twelfth grade.