Indeed there's all kinds of Montessori.
I can vouch for my daughter's .
If anybody wants to give it a go, my benchmarks are:
1) find reviews of parents, especially no abuse, shouting, kids in the last year should LOVE the place.
2) observe even for few minutes a class in their focus time -- you will feel almost shocked if you haven't seen this before -- like you entered Santa's workshop -- children should be deeply engaged in their activities. If you haven't seen it before you might suspect abuse (that's why point 1 is so important), no way kids love to wipe the floors, lay tables, prepare food and so on, but they actually do.
And all that done in almost complete silence.
Proper Montessori with good, empathetic, dedicated educators is amazing!
Different levels of Montessori authenticity make the results even more impressive. They do have some inclusion criteria, like 2/3 of the teachers must be AMI/AMS certified but even so I'd expect a lot of these public school montessori programs to be less "true montessori" than what you'd get at a fully certified AMI/AMS school.
Who cares? It's not about me or someone else (or you), it's about the issues at hand. If the commenter wants to make a claim, they are welcome to.
People on HN can't read a study without finding one of the few methodological flaws they are aware of - as if that's some form of serious analysis.