Full results here
1. Adlai E. Stevenson High School B - (70)
2. Carmel High School A - (128)
3. Ladue Horton Watkins High school A - (141)
4. University of Chicago Laboratory Schools A - (212)
5. Sylvania Northview A - (221)
6. Carmel High School B - (223)
7. Crystal Lake Central High School A - (224)
8. St. Ignatius High School A - (243)
9. Lyons Township High A - (257)
10. Waubonsie Valley High School A - (271)
Oddly enough, while there is a Stevenson B, Stevenson A is missing...
I've seen a few B teams outperforming A teams recently (like at MIT: Solon B over Solon A, Conestoga B over Conestoga A, Troy B over almost everyone) and I assumed it was a coincidence. Maybe its a joke? After all, the A/B/C denomination is pretty much arbitrary.