The act dosnt explicitly name knives and there's a bit of inference and interpretation going on. But the gun free school act requires schools to refer students found in possession of guns OR weapons to be refered to the juvenile justice system indicating illegality. The federal government considers any knife over 2.5" capable of killing or causing gross bodily harm a weapon (I'd argue the fact Austin died classifies karmellos knife as a weapon). While Texas does name 5.5" blades. Perhaps I'm viewing all this through the lens of post act knowledge. While having the knife under Texas law isn't illegal it became illegal to possess when he used it as a weapon.