Hi, A.,
I concur with most, if not all, of the suggestions already given. As a former teacher (mostly high school) who taught for over ten years, I would recommend observing the STUDENTS at the school as much as allowed by the administrators. I think teachers play an important role in a child's life, but I think that classmates play an even more important role in a child's life than do his teachers.
In addition, drive or walk through the neighborhood in which each school is located. I've found that no matter how much a school is touted, rich people, whose kids, on average, tend to do better academically, possibly because of access to more and higher quality services in life, won't send their kids to a school they consider "down and out" and thus unsafe. Even when it comes to private schools, generally, kids who come from more affluent families and will provide more academic competition for your child will stay in more affluent neighborhoods, and kids who come form less affluent families, even if offered a chance to attend school in a rich neighborhood, will not attend the schools in those affluent neighborhoods, which almost always offer a child more academic competition. I am not saying that all children who attend schools in poorer areas will fail school or life. A few times, I've seen some kids in "poor" schools, including private schools, do amazing things, like doing all their classwork while classmates were running in and out of class, yelling, vandalizing property and stealing teachers' possessions, because they were internally motivated.
Also, talk to as many parents of students at that school as possible. (Try to find parents who are satisfied AND dissatisfied with the school.)
If you really want to know how much your child might be challenged, try to talk to some teachers, including new teachers that have the least academically advanced class in a particular grade. Find out how much homework the teacher assigns and how much of it is actually completed and how well it is done by all his students. Teachers have less incentive to paint a pretty picture than do most principals. (That being said, I find some principals, especially in public schools, refreshingly honest and modest.)
Ask the principal how many/what percentage of teachers at the school have a California Clear Credential, not just an Emergency credential. Generally, teachers who possess a Clear Credential have more training and more experience than those who do not.
Don't assume that sending your child to a private school will prevent or even reduce the chance that he or she will smoke, use drugs, have sex, etc. Several people, including my husband and co-workers in various industries, have told me that they were sent to private school to "straighten out," meaning quit smoking, using drugs, behaving badly, etc. and that they found more of their kind in private school! My ex was sent to private school and my ex's brother went to some great schools, but they still found ways to be "bad" and people with whom they could do those "bad" things.
When your child is nearly old enough to enter high school, find out how many of the students at the school that year took Advanced Placement (AP) courses AND passed the Advanced Placement exams. Principals like to brag about the number/percentage of the students at their school were enrolled in AP classes, but this number/percentage is meaningless without the number/percentage that passed. At my last school, the principal loved to tell parents of students or prospective students how many students were enrolled in AP class but, at least when I was present, never informed them that ALL of the students in some of the courses, such as AP Chemistry, in spite of having superb teachers, failed the AP exam. The number/percentage of students who take Honors courses is meaningless as Honors can be defined however the faculty and administration desire and thus varies greatly from school to school.
In deciding where to send my children, I will consider not only the academic standing of the school but also the range and quality of extracurricular activities. If my children seem very happy doing only schoolwork, especially that in core academic subjects, such as math, English and history, then extracurricular aspects won't matter much. However, if this is not the case, then I will consider the breadth and depth of the extracurricular program in deciding where to send my children.
Good luck in helping your son find a good fit!
Lynne E