Often, the parent that has the child during the summer learns information from the child that causes the parent to be concerned about returning the child to the school placement parent for the beginning of the school year.
If you find yourself in this situation, I recommend that you document the facts and the circumstances that are creating your concern. Secondly, I recommend contacting an attorney immediately to determine your options to file an emergency motion or at a minimum a motion for modification of your parental rights and responsibilities.
As you may already be aware, the courts process motions very slowly. If you have grave concerns about your child returning to the other parent for the beginning of the school year, emergency motions must be filed as soon as possible. If you do not return the child at the appointed day and time, in violation of the court order, a contempt motion may be filed against you and the police may be called to enforce the current order.