Having to suspend or expel a student for defending themselves never feels good.
If they are expelled for defending themselves the policies need to change. The cameras should provide evidence they were defending themselves. When enough violent kids are removed the incidence of having to defend one's self should be reduced with time.
That's the point though; zero-tolerance means that the cause doesn't matter. Defending yourself means you participated in violence and you're punished for it. Zero-tolerance is a horrible idea in general, and only sense in the context of protecting the institution from liability.
In this case it's not really Texas 'not allowing' other states to help but the other states not allowing Texas. Conceivably federal law could be updated to remove those regulations and Texas would absolutely connect to the interstate grid at that point.
That, of course, ignores the fact that those regulations are in place for a reason. Texas refuses to play by the rules, and the impact of that is that they don't get help when it's important. It is unfortunate, but a direct consequence of the choices they made.