More information is needed. A good personal injury lawyer in your state should be retained to investigate to see he can get around any school immunity statute many states have.
You have not provided enough information for me to fully answer, but if the teacher intentionally injured the child, the teacher could be personally liable. If the teacher had previously intentionally injured other students, perhaps the school district could be liable for keeping the teacher employed after a demonstrated propensity to intentionally injure students. As a general rule, though, school disgtricts in most states are immune from injury lawsuits in most cases. That may not be fair, but unfortunately it's the law. AVVO probably has an attorney with a listing in your area, and I suggest you consult with a lawyer.
First and foremost, schools in Texas have almost absolute immunity and are not generally liable for the acts of their employees.
That said, whether the school or teacher might be liable here would depend on the specific facts around this incident.
It sounds as though your child is disabled as defined federal law. If so, and if the teacher's abuse of your child was related to that disability, the school district might be liable under federal law.
If the teacher injured your child in the course of punishing him, the teacher might be personally liable under state law.
This is for informational purposes only and should not be considered as legal advice. This communication does not create an attorney-client relationship. Without knowing the specifics of your situation and prior to engaging in an attorney-client relationship I am unable to provide specific direction.