Grade 12 has it the easiest by far lol I didn't care about my grades as a senior and I don't think my college even saw any of my grades from my senior year. If they did then they didn't see it until they already accepted me.
I don't think people bully near as much in high school as they do in middle school. Some of the upper clansmen I guess may not be as willing to talk to you. When I was a freshman I had friends of all grade levels and they didn't care that I was a freshman. When I went from freshmen to sophomore to junior to senior each year I found myself being more acceptable and willing to talk to freshmen.