The Georgia High School Swimming Awards

"The 2018 GHSA Swimming and Diving State Championships were held Feb. 1-3 at the Georgia Tech McAuley Aquatic Center." 

No mystery in that, except GHSA (Georgia High School Association). But there's quite a mystery in how they divide up the teams.  I couldn't find a glossary anywhere on the website. 

Here are the winning teams.  Can you figure out how they're organized?

1A-3A: Westminster School, Atlanta. 




A private school, founded in 1951 but tracing its roots to 1853 (when a Presbyterian girls' school founded on the site).  It has "the largest endowment of any non-boarding school in the U.S."










Then we skip directly to:

 7A: Brookwood High School, Snellville, GA, about 30 miles northeast of Atlanta.  Their wikipedia page helpfully tells us that classes start at 7:24 am, when "more than 40 buses" arrive.


















Next it's down to:

6A: Dalton High School, Dalton, Georgia, about 90 miles northwest.  Its principal is Steve Bartoo, and its mascot is a catamounts (some sort of leopard).

Dalton, population 33,000, is known as a center for floor covering manufacturing.







It's also the home of the Georgia Athletic Coaches Hall of Fame and the Northwest Georgia RAW Powerlifting Contest.







Next:

4A-5A: St. Pius X Catholic School, northeast Atlanta, near the airport.  One of the more prestigious high schools in town, its students win numerous academic awards.















Some more award winners.


So: geography? 
Public/private?
Size?
Prestige?
Type of swim trunks worn?