The Chaos Class Is Fretting Over(1979)

Lazy, uneducated students mostly coming from money, share a very close band. They live together in the dormitory of this private highschool, where they daily plan their latest pranks on teachers or the other classes. When one of the students get his girlfriend pregnant, the whole class acts together to help him. The mother has to leave the baby for a while with the father, and this leads to a series of funny events.