This isn't an airplane... You can't just oversell the seats. Student tickets are not currently standing room only tickets therefore you can only sell how many seats are available. Now if you wanted to create standing room only tickets for the catwalks then go for it, but that is a completely separate thing.
Your issue is with student tickets not being used, not not being scanned (meaning the student was at the game but their ticket wasn't scanned). You can't force anyone to go to the game instead of just tailgating. Just like you can't force them to stay past halftime or the third quarter. Just hope the team keeps doing well and the problem will solve itself.