Hi Samir,
I've just got back to the UK from a school in Florida and am planning on going back out there later this year so was asking about this while there.
From what I understood of it you will have to give your fingerprint as you pass through immigration at your port of entry, as everyone now does. You will then have a certain amount of time (three days I think) to register with your school and go to the local Sheriffs office to register there which is where they take your fingerprints again.
As I said this was the information I managed to get hold of whilst out there but not sure how reliable it is. Try checking with the school your going to, they should be able to confirm it. The dear chaps at US Immigration aren't too keen on bending the rules so make sure you've got the right info before you head over there or you'll be straight on the next flight back home.
Good luck with it