See this article from Peter Sims
which talks about how Montessori is at the core of establishment of organizations such as Amazon and Google.
The most important thing is that the school should have certified and trained Montessori teachers.
is the next important thing. The school should have infrastructure and technology to track individual progress. At this tender age, every one develops at his and her own pace. The technology should support development of milestones, track it and help plan for it.