OMGGGGGGG, all I have to say is that I was in that EXACT situation, lol. Wow... Only I didn't give her a note telling her I liked her...
I mean, you even have the same class size as me...and when I was one of a few kids not to go on a clas trip she noticed I didn't go.
What I would do is just maybe sit next to her in classes - but not all of them - then she might think your stalking her, lol. Also try and talk to her in the hallway, and if you walk by her anywhere be sure to say atleast "hi".
...The problem also is shes very popular and im not really friends with her friends, i only have 2 friends in my class but she knows everyone in class.
What has that got to do with anything?
If she likes you, then it's you she wants to be popular with.
If you like her, what does it matter how you get on with her friends?
Acttually, I see why jam posted that. I was thinking the same thing. I was wondering why a popular girrl would like me...cuz I'm not so popular. You know what I mean? I would always think that they were playing a hoax on me or something.