First year was hell. Right out of a TV show, with the popular kids picking on the unpopular nerdy kids (i.e., me). In response, I was angry and shut off to all of them, and quite often got in trouble, either for lashing out or for simply not going to classes where I knew I would be picked on and the teacher would do nothing. Most people pegged me as the next major school shooter, but that didn't stop them from making my life hell whenever they felt like it. Even the teachers joined in.
10th and 11th grade were better... I had some friends, and people for the most part didn't bother me. However, the leader of that group of friends was intensely critical of me and ended up just using me for money, and because of her actions, our group more or less fell apart. Also, the school started to realize I wasn't just a "problem child," but an asset for them once I stopped being pushed around all the time and feeling like I was under attack, so I had some more leeway. Still some power struggles with teachers, just not as bad.
12th grade was probably the most stressful in terms of things going on in my life, but socially the easiest. Both the school and my peers realized that I was really smart and I could be of help to them given the chance - the school knowing that if they stopped fettering me with all these petty regulations, I could be everything from their school pianist to their science fair champion to the person most likely to go to an Ivy League-level school, and the students realizing that if they were nice to me, I would proofread their papers and help them do well in group projects. Also, a couple of students transferred in that year, and even though they were popular kids, they were the good sort of popular ones, and made an effort to be nice to me, which helped in the general student body's perception of me.
I ended up graduating with a 4.3, getting accepted into a lot of the schools I applied for including the one I wanted to go to, Smith College, winning 2nd place in the County Science Fair, becoming a National Merit Finalist, winning an award in History and performing piano at my graduation. I definitely wouldn't repeat high school, but parts of it were not nearly as bad as I had expected in my freshman year.