I’d take the part out about being pretty; something like 'Hey, I liked what you said about X in class the other day, want to go get a burger and talk more about it?" is better. If you don’t have a class with her, then “Hey, I’ve noticed (you wear tshirts for X tv show, you listen to X band, you were talking with your friends about X movie, you’re on the whatever sports team); I’m interested in that too! Want to get together and talk about it tomorrow after school?”
I absolutely, 100% agree with everything phouka said. If you’re even a small percentage as needy/desperate in your real life interactions as you are here, you’re pinging every subconscious alarm that girls have. Just reading your posts makes me uncomfortable. Your constant repetition of ‘I’m desperate to have a girlfriend/I don’t want to be one of THOSE guys’ implies that you’re not looking to date for the sake of getting to know a particular girl, but rather to check a box off in the life category- and I promise that that comes across IRL. The best piece of advice I can offer about dating is if you can’t stand to be with yourself, you can’t really expect others to stand being with you on an intimate level. Work on yourself first- particularly your anxiety- and the rest will fall into place.