Seniority.

Seniority is something you need to respect. The only time it becomes a problem is when underclassmen start to step over their boundaries. In middle school, when sitting on the bus, I used to always get so frustrated when the older kids would make such a big deal about the back of the bus. We were all going to the same place, what was the big deal? This was the big deal, they needed to feel bigger, they wanted to have power over the little kids. Now in high school it gets better, it is not as big of a deal because people start taking classes together and the maturity levels grow to be on the same plane. However, seniority  is still a big deal to people, especially in football games and in drama and other things. This is my best advice when it comes to that, if you make the most of wherever you get to sit, and be humble about positions or places you get over an upperclassmen. Here are some other pleasant gestures you could do for upperclassmen:
Give up your seat for them at sporting events
-Cheer loud for every team (this is one of the seniors largest pet peeves)
-Congratulate everyone in everything they do (people deserve the credit for all the work they have done)
-Know that you will soon be the ones who sit in the front
You will get older, give it time.
Now being an underclassmen once before, I understand the frustrations that come along with the idea of "seniority". Even as someone who supposedly one who has the power over underclassmen. This  is not a power I use often, or at all really, but I appreciate when it is acknowledged. But as I said because I have been an underclassmen, as an upperclassmen, I do my best to treat underclassmen just like anyone else, as long and they know that I may be a bit older and wiser than they are. It has been working for me so far, so keep that in mind when you discover how agitating the underclassmen can be. Rather than being meaner than is necessary when you get to your reign of power, remember you were once in their place too.
JSL