It depends what state you're in. In WI, covenant not to compete clauses DO hold up in court and have already been tested and won. Reasonable as determined by the courts in our state "while working & for 3 years after for a 20 mile radius". Contact a lawyer & get the wording right. You also can put in a confidentiality agreement in there which states that they will not take curriculum home or take personal contact information of your students outside the studio. That way they can't call everyone up to say that they are opening a new place, or solicit your clients directly.