An individual one

Headmistress: "You assaulted Alexis so it is only fair that she gets to decide of your punishment. To ensure that you comply with the punishment she chooses, I will give her your key and she will give it back to you once she deems that you have atoned for your wrong doing."

She calls Alexis to her office over the tannoy and explains her what's going to happen, which immediatly put a wide vicious grin on Alexis' face. The headmistress gives Alexis your key and the two of you exit thd headmistress' office.

Alexis : "Oh this is just great. I already know what i'm going to do with you and your key."