Corporations use non-compete contracts for their higher level employees. My father was in management and had one. They don't usually do them for office staff and other loewr level employees. A manager could potentially take clients if they left the business to start their own; lower staff probably wouldn't. A teacher is like management, they have constant contact with your clients and relationships with them. A non-compete contract is not a bad idea as long as it is reasonable. But you don't need to have assistants sign one.

If you are in a small town with 2 or 3 studios you NEED a non-compete contract of some kind. In a larger city it is harder, especially if you cannot keep a teacher busy. It would not be unreasonalbe to give a radius in which they may not teach, say 15 miles from you. That would still give them options of other places for employment. Or say that they must have approval, then you can sa no if they want to go to work for your biggest competitor.

You should ALWAYS consult a lawyer if you are considering having employees sign a contract. I have taken business law, legal liabilities, and a few other law classes and I know enough to know when I need a lawyer. Taking a business law class or a contracts class helps you understand your needs as a business but does not qualify you to do your own legal work. If their are states that don't hold up the non-compete clauses you need a lawyer who will tell you what you can do instead. There will always be an option.