If I allow my daughters father to enroll her in his school district, can I put in a written agreement that the child support order stay the same

You may enter into a written agreement with your daughter's father, but it is not binding on the court and either of you maybring a suit to modify the terms of your orders regrading your daughter.  It certainly is not binding to agree that neither of you may file a new claim. If your daughter is going to be spending more time with her father and less with you as a result of the school change,  the father may file to modify the primary conservatorship and request that you be ordered to pay child support. This is true even if the father signs something stating he won't ask for the support to change and won't try to obtain custody.