Well, that depends mostly on the person and opportunities to get
>> these qual's << signed off. Every qual' that starts with the #4 is one he needs signed off before he can advance to E-4/BM3. And so it goes - 5s are for E-5/BM2, 6s are for E-6/BM1, etc.
Striking is the toughest because it requires the E-2/E-3 to continue doing his/her "day job" while trying to get qual's signed off. Some can be signed off during the course of a day's activity, some cannot. Not because no one wants to but rather other people are doing their "day jobs" too.
A school allows the individual to get all requirements for E-4 signed off while concentrating solely on those factors. The A school attendees whole job is to focus on academics and practicals.
Disclaimer: I'm not a doctor or a recruiter. Verify any and all information I've stated before making a fool of yourself.