Escape from Women's Prison(1978)

Original title: Le evase - Storie di sesso e di violenze

Four female convicts break out of prison, and during their escape they take hostage a bus full of young female tennis players. They drive the bus to the house of the judge who originally sent them to prison, where--since this is after all a women-in-prison picture--the hostages undergo various forms of physical and sexual abuse in various degrees of nudity.