Quoted:
in PA for athletics it goes...
A - smallest schools
AA - small schools
AAA - bigger schools
AAAA - biggest schools
More correctly, it is the size based on gender and for some sports depends on if the school has a "freshman" team. For example, a school for 479 boys in the 4 classes (freshman through senior) would be Class AAA. However, if the sport is football and the school has a freshman team then only the male class size of the uper 3 are counted against classification (sophomore, junior, senior). So, a school with 479 in the upper 4, minus 120 for the freshman class would equal 359, placing them in 3AAA size. Women's sports are then classed on the number of women along the same lines. So you could have a school which plays baseball in AA but the girls play in AAA in softball. Of course each school can also elect to play one (or 2 maybe) classes above them (ie: a Class A mens basketball could elect to play in A, AA or AAA).