You should talk to her!
May be something like this can give her a hint:
" Look, I really like you, I am confused but you have occupied for quite a part of my life. But my heart is half devoted to you, and another half to my future...." May be you can think of longer sentences?
You may consider study a common subject together with her. Try to listen to her complaints about schoolworks, making jokes at despicable and mean teacher.
Just give more information and see what can I help you, my friend!
You know what I fear? I fear that your infatuation is just temporary, a month later who know, you may accuse yourself for being so foolish to put all your brain power in a girl, while she's not the one you have thought of. Why don't you try to re-examine your own feelings for her, you know.