start conversation with him by facebook, then try to meet with him outsider your school, go to a coffeeshop or a park (a nice place...) and spend some time with him, get to know him well, find out what does he like, send him 1 sms per day asking how's he doing, blah blah. don't be shy. the "no" is certain but you can get the 'yes'
believe in yourself.