PWN! I've had that little issue happen to me a few times as well. It's not really a big deal. At least they were "polite enough to let you sit there," right? If it's that big of a deal, you can always speak with the offending upperclassmen about it. Then, if the problem somehow manages to escalate, you could involve your father or the principal. But honestly, what does it really matter? It's a table in a highschool cafeteria.
