Disclaimer aside, the results of the study are dramatic. I have included the graphic from the article on Jonah’s site since the Science link requires a subscription.
“On several dimensions, children at a public inner city Montessori school had superior outcomes relative to a sample of Montessori applicants who, because of a random lottery, attended other schools. By the end of kindergarten, the Montessori children performed better on standardized tests of reading and math, engaged in more positive interaction on the playground, and showed more advanced social cognition and executive control. They also showed more concern for fairness and justice. At the end of elementary school, Montessori children wrote more creative essays with more complex sentence structures, selected more positive responses to social dilemmas, and reported feeling more of a sense of community at their school.”
It is interesting that the one area of challenge for the Montessori kids was in “ambiguous rough play.” Part of the issue might be how the groups are compared across the same grade levels and the Montessori philosophy mixes the kids across age groups; younger kids would need to learn more aggressive techniques for dealing with older kids than when interacting within their own age groups, and when later compared to other kids in the same age groups might come across as too aggressive. On the other hand, there just might be discipline issues within the more permissive environment.
Overall, I think most school curricula need a little more of the exploratory Montessori flavor which fosters personal hands-on experimentation. The real question in my mind is how to encourage this without loosing rigor and discipline in these activities.