West Valley Middle School (WVMS) is part of the Action Day/Primary Plus private infant - 8th grade set of daycare through secondary school campuses. (There are many campuses for daycare and preschool, and there is a single campus for each the elementary school and for the middle school.) Our family has no experience with the preschool or infant rooms.
My younger son is now at the WVMS campus, after having spent 2 years at the elementary school Primary Plus Amber campus in San Jose. During his elementary and secondary years, my older son, now in high school, was a student at a couple of well known private schools, one in Palo Alto and one in Saratoga. Frankly my younger son's overall elementary experience is tremendously better than my older son's. Primary Plus is amazingly underrated and I wish I had known about the school when my older son was younger. Primary Plus does more than "have a philosophy," classroom curricula are integrated throughout the campus, and academic and artistic/whole child teaching occur for all disciplines. Finally, my younger son is clearly learning a tremendous amount, academically, artistically, and socially, and I know from comparing his work to that produced by students at my older son's former schools, that he is well ahead -- and without feeling pushed or pressured.
One difference from other private schools we've experienced is that there is little social interaction between families at the school, and that this is by design (i.e. discouraged by upper administration). While this will be a drawback for families who want to become a part of a broader school community, again, our experience is that the focus is on the children and on having great teachers, a large percentage of whom have been present for over 10 and as many as 25 years. (Also - obviously - we've been able to connect with other families away from the school.)
Finally, the tuition for the elementary and middle schools, while more than at, say, Catholic schools, is very much less than at the schools mentioned above in Saratoga and Palo Alto. Maybe it's more in line with chain schools like Challenger, I'm not sure. (Thankfully, the elementary and middle schools are not part of a chain, insofar as chain schools tend to dump lower performing students - which sends a bad message to children. In fact, the small environment at ADPP and WVMS means that, within a range, learning differences can be accommodated well.) But the classroom experience is excellent, and the students who graduate from 8th grade go on to a number of great high schools. If what you are looking for is a great education in a caring environment by experienced and dedicated teachers, at a cost that won't send you reeling, take a look.