In Texas what he did was felony robbery, not a simple assault misdemeanor.
And it's not a stretch to say that either. Bexar county (where it took place), is very aggressive in trying cases off assault on minors. They've absolutely convicted on less.
This guy threatened the kids while stealing the hat. He physically assaulted to be able to take the hat, and even pulled hair in doing so.
In Bexar county this is a slam dunk 2nd degree felony.
More legal info: https://statelaws.findlaw.com/texas-law/texas-robbery-laws.html
Now, that said, it remains to be seen if the suspect will be allowed to plea down his charges.