Harenchi Gakuen summary:

This is the legendary Go Nagai's breakthrough work. Harenchi Gakuen is an elementary school whose teachers and students are all perverts. Boys peep girls changing. Girls pull up their skirts and show off their panties. Actually, it's not as evil as you imagine. They're like cubs playing together. It's only pre-school eroticism, nothing sexual. In spite of that, Harenchi Gakuen became a sensation. Parents, teachers, and politicians hysterically attacked the comic's immorality.