How many movies have Joachim Hackethal and Walter Boos collaborated on?

They have worked on 4 movies together! Their first movie together was The Swinging Co-eds (1972) while their highest rated movie together was Schoolgirl Report Part 10: Every Girl Starts Sometime... (1976). They have not worked together since Schoolgirl Report Part 10: Every Girl Starts Sometime... (1976). They are most known for their comedy films together.