Oresama teacher is the funniest manga of all time!
Kurosaki Mafuyu was a juvenile delinquent and head of her gang when she was expelled and transferred to a new high school, she decides to become and let me quote "an ultra-shiny, girly-girl high school student"
Then she makes her so called "first friend"
Then she realises that her teacher is non other then her childhood friend that forces her to join the Disciplinary Club
Suddenly a ninja appeared who joined the Disciplinary Club and so the three become friends.