I'm definitely affected by certain songs. Funny story ... When I was a kid, the song "When She Loved Me" in Toy Story 2 did me in all the time. I was a sensitive kid and treated my dolls like they were my children, so the thought of Jessie's owner abandoning her made me weepy. Once my school got to see Toy Story 2 as part of a special day. I was soooo nervous because all I could think about was how much that part of the movie made me cry, so 4th grader me devised a brilliant plan—I told my teacher I had to go to the bathroom a minute before that scene started. I timed it right and hauled myself to the bathroom, but once there, I simply replayed the song and scene in my head and wound up in tears anyway. Fail.

Sometimes the memories associated with the song are worse than the mood of the song itself. The song could be upbeat and happy, but if it provokes an intense memory, I can't stand it. For instance, one of my exes loved the song "Like I G6." Whenever I hear it now, I think of him and remember how much of a jerk he was. Luckily I never cared for the song in the first place. :P

I agree with Resident Bipolar's suggestions. Bring something to drown it out if possible, and do talk to the school. Bipolar II should qualify you for an IEP or at least a 504. The school would then have to provide you with whatever other supports you feel would help you succeed throughout the day. I had a friend in high school who had bad migraines. The fluorescent lighting and the noise of the cafeteria triggered them, so she was allowed to eat in a quiet place as a part of her 504, and I was allowed to come keep her company, so she wouldn't have to eat alone.

Maybe you could keep a song mood journal too. Every time you have a strong emotion or memory associated with a song, jot it down and bring it to your next appointment with your therapist. Sometimes getting something out on paper helps me immediately, and if the song is especially triggering, maybe you and your therapist could listen to it together and work through the emotions.