Maybe Charlotte could have her class do a project on the scientific identification of witches. You can't kill them until you know who they are.
Witches are an odd lot. They claim to have certain powers that they deny having when dragged into court.
I worked with a witch one time. She threatened another employee with a hex. He complained to management and hilarity ensued. Management couldn’t dismiss the accusation because of diversity measures. The witch had to admit that hexes weren’t real so it wasn’t an actual threat.