Picking a HS is like shidduchim; references are a good starting point, but to really know if you have a good match, you need a face-to-face. Then, its Syata Dishmaya till graduation day, because HS is make it or break it, and do-overs are real costly ($ lost time and eaten kishkes)
When we were in the deciding stage, once we had the list down to 3 choices we did the following:
1) Went to see the school at lunch and dismissal (to see the boys in their natural environment and
2) Went to the school melaveh malka (to see the parent body)
Again, nothing is a guarrantee, but where hishtadlus ends, syata d’shmaya (hopefully!) picks up.
And like a shidduch, all look promising, all have their pro and cons, but you can only pick one. Pick the one you feel is the best fit, and commit youself to working till you drop to make it work. Them, pray like your pants are on fire. That usually helps, even if you somehow missed something.
B’hatzlocho!