[math_denial]

I think the success stories are mostly self-selection: parents who care enough about education to enroll their children in an alternative system will have children who care more. Anecdotical data: in my non-US state everyone (admittedly 3 people) who went to Montessori schools were 3 years behind in every subject as compared to public schools and mostly they did fine with some help, but the difference between who did better or worse was, as you pointed, inherent personality that was completely independent from the education they received.

[olau]

There is of course self-selection compared to going with the default, but your data may be poisoned.

I don't know the Montessori system, but in the Waldorf system, some of the intellectual stuff is moved from the first years to the later years compared to the public school. So if you compare midway on the public school metric, you'll find a gap.

Of course, if you compared midway on a Waldorf metric, you'll find that students from those public schools have a gap in the other direction.

I talked to a Waldorf school principal about this, and she said that if you enter the system at later grades, say halfway through, they could see that there are some things that such a child just don't learn.