I'm pissed at my Teacher, What should I do. (10 pts)?

In our band, we have two different cles. The advanced one, called Wind Ensamble, and the less advanced one called Concert Band. I'm currently a sopre, and We were getting our cl for next year, I was 1st chair all year in my section, in CB, and just last week i was moved to 3rd chair because I wasn't attending the School Band Trip (***Note it costs 2,000 and it ISNT mandatory.) My family couldn't afford it with my house just getting remolded and my sweet sixteen coming up. Anywho Me and my best friend are 3rd and 4th chairs out of 18, and 3 people from our section are moving up, out of 18.!). I was once again put in concert band, and Not wind Ensamble. When I asked Why, he said because I was tied with another player (My best friend, and a worse player than me.!) because I'm not going to Florida(THAT WASN'T MANDATORY) and because I missed one practice, and a game later that day, (BECAUSE I HAD A TORN ACL IN MY KNEE and I didnt see the need to go to practice and a game then.?) and she hasnt missed a thing. This is an IN SCHOOL CL. and on top of that....I'm the band directors istant. What do I do.? I'm sooooooo PISSED. I'm going to be the only Junior in a cl of Freshman and all of the freshman who are my friends got in. -__- I was even asked to do the accomp. for the choir concert. So clearly playing isn't the issue, and we march together for marching band, What do I do.? HELP PLEASE.!(: