Cars and more cars.
Either those cars were given to the kids or there were plenty of part-time jobs because those kids had money. I went to high school in the mid 60s and some kids had cars but not the parking lot full shown in this movie. The insurance alone was $1.00 a day which sounds cheap today but it wasn't back then.
"You may as well go to perdition in ermine; you're sure to come back in rags." Katharine Hepburn