Forty Little Mothers.

Gilbert Jordan Thompson stops a suicidal stranger from jumping off a pier and helps her get a job. He finds an abandoned baby with a note asking someone to give him a good home. When he can't find anyone to claim the baby, Gilbert "adopts" him so he won't end up in an orphanage. Soon Gilbert gets a teaching job with live-in quarters at an all-girls school that doesn't allow teachers to have families.