There are literally dozens of alternative school models throughout the world, and I've done research on a lot of them when I had my kids. What I found was broad and varied. Different results, different opinions from parents and former students, different conclusions from researchers. Both on the positive and negative sides. I never got to make up my mind, and I ended up putting my kids in a public school in a small town where there was only one school per age segment. It's a pretty good public school, probably like a good private school, but there's a difference in that the student body is truly varied. My kids study with the son of the garbage collector and the daughter of the supermarket owner. There is a Waldorf school not too far from here, in a neighboring town, but it's as diverse as a very expensive school with everyone arriving in imported cars can be. So I chose not to put my kids there.

edit: Plus, I'm not too fond of Waldorf's philosophy, and even less of the Anthroposophy's.