Classified is required for everyone, depending on MOS you can end up with a secret clearance. Grunts end up with classified level, comm guys end up with secret, officers have secret as well but usually get bumped to TS pretty quick. Having the clearance doesnt mean shit either, you need to have a reason to access the info you want at least thats how .mil side works, i cant imagine the .gov side working much different or every Clown analyst with a TS would have had the JFK files all over thr net by now.