It turned out he chose to attend the boarding school 5 blocks from my house that doesn't require SSAT, but has its own entrance exam. It's going very well for him. Plus he received almost a full scholarship. He's excited that he'll take 4 college courses senior yr (it has a jr college too) and credits transferred and he played varsity soccer (while older brother didn't get as much playing time at the local HS).
This sounds like a solid option with plenty of opportunities! Congratulations on his nearly full scholarship and especially the five block commute!