No. In the 1990s, the Texas Supreme Court looked at the issue of whether or not the parent could enter into such a contract on the child's behalf. They held that a release of liability pre-injury, signed by a parent of the injured child was void.  The logic behind this decision was that it was a matter of Texas public policy to protect children--even from their own parent's actions. Thus, any contract attempting to give up the child's right to bring a claim against someone for their future, yet unseen, negligence is void.