Legal Question in Family Law in Texas

If he is a blood relative, you can file a Authorization Agreement for Non-Parent Relative and that will give you all the power you need. You can get a free form from my web site (under Resources, Free Forms, Authorization Agreement).

If he is NOT a blood relative, you need at the very least a letter from his parents authorizing you to obtain medical treatment for him (you will be on the hook for the bills) and a letter from them to the school saying he is living with you, which should allow you to enroll him. Technically, I don't think the school is allowed to refuse his enrollment, but they might challenge it later, particularly if he is an athlete and an opposing team wants to make him ineligible for some reason.

On the far end of the scale, the parents could consent to you becoming a managing conservator of the child, but that is like shooting a mouse with a bazooka. It will solve the problem, but it's over-kill.

Good luck!!