What should I do about this guy?

Last year in year 9, I had the same lessons with this guys 3 times a week. He was really nice, we would talk and joke all the time. In the middle of the year, I started getting a big crush on him and I would really look forward to the lessons we had together. One lesson, I started flirting with him and I was so happy when he started flirting back with me!! We carried on like this until the year ended. We parted for the summer and I was really upset at the beginning of the year when I found out we didn't have any lessons together this year. Over the summer, every girl had suddenly decided he was good-looking so now he always has a crowd of girls around him. At the beginning of the year, we would stop to talk in the corridors, then it just went to 'hi', then to just smiling at each other in the corridors, now he barely looks at me. And I still really fancy him!!I don't know what to do!! I don't want to give up on him, I like him so much! Help me!!