How do I choose the right school and instructor?
It boils down to one question: Do you feel comfortable entrusting your child with the instructors? A good kids' instructor needs to have plenty of patience and should be both entertaining and in control of the group. Try talking to other parents of students about their experiences and - most important - visit the potential schools and watch classes at each one before enrolling your child. If the instructors won't let you watch, it's definitely the wrong school for children.
Don't be afraid to ask questions. If you're worried about an overly aggressive environment, ask how the school addresses self-control, conflict resolution, and issues of respect. Then watch, especially during sparring sessions, to see if the teachers walk their talk. Make sure you're entirely comfortable with your decision.