Well compared to other inner London schools which I've known 10 leaving at the end of the summer term really is a normal number Unlike other jobs, teachers generally only move at the end of terms and usually most in the summer. Charter is lucky in having no problem attracting very good staff, but that does mean they tend to move on and up quite quickly. My experience of charter staff is that they enjoy working there and moves are almost always for promotions or because it's difficult for them to continue living close enough and have a family.