No. There is no set number for classifacations. Your enrolment can stay the same, yet you can move up. If your enrolment is in the middle third of all the schools, you'll be in AA... Say if you had 510 kids in period 1, and you were in the bottom third of schools, you'd be in 1A. But in period 2, if your enrolment is still 510, but a few schools lose alot of kids, and a few smaller schools join the T$$AA and that happens to bump you up to the middle third, your stuck in AA.