Answer:
I have a mouth on my head and eat everything.
You kick me, you punch me, and you beat me up all class. When you leave, you don't even say thanks for allowing you to beat me up. What am I?
My keepers feed me colored balls. With sticks they store on my den walls. Sometimes I store them in my pouch. Sometimes deep in my belly; ouch!
I am lighter than air but a hundred people cannot lift me. Careful! I am fragile!
When you stop and look, you can always see me. If you try to touch, you cannot feel me. I cannot move, but as you near me, I will move away from you. What am I?
It has no top or bottom, but it can hold flesh, bones, and blood all at the same time.