The virtual world is full of truth and untruth. Even though you
and her is from the same school and level, it doesn't make her
natural defenses any less. She might think you are one who always
talks to girls online. And many more (only girls can think of those
crazy ideas. I'm not a girl, don't ask me. Maybe FeowFeow?
). Take it one step at a time. Get to know her more
and make sure she gets to know you more. You can easily tell if a
girl you talk to is attracted to you. A simple thing like "you too
hors.. sleep early hors.." can mean that. By the way, i would
encourage you to use MSN rather than SMS. SMS ensures that if the
girl is polite, she would reply you and you two can have a long
chat. MSN ensures real-time response and to me, more intimate than
SMS. But FTF is still better. Phone comes second. (unless you and
her have 3G phones. Video conference. Then i have nothing to say.)
BTW, you're in the same school with her, right? Then maybe get your
presence a little more noticed by her. Try to appear within her
sight, etc.
So, summary. Talk to her on MSN more often. Drop very mild hints
every now and then. (my every now and then doesn't mean once every
day. It means once around 4 / 5 days.) Try to register your face in
her mind.