The key to a successful and meaningful contract is to create it with the company, not for them.
When working with young people on any project, a contract is a fantastic tool to have. You set out your standards and goals early on and ask everyone to sign up to it. It can influence everything from the structure of your rehearsal to the way in which the group communicates. You can then reference it throughout the process, ensuring that everyone lives up to their side of the bargain.
The key to a successful and meaningful contract is to create it with the company, not for them. Having them set the standards and propose additions to the contract themselves makes them far more likely to stick to it, especially if you highlight that this contract applies to you as the director as well as them.