It also had an obvious and unhelpful result. Of course kids who spend all day learning will know that stuff better than kids who don't. What really matters is long term life outcomes.
Rudolf Steiner would say all that early learning is harmful and they should have been playing and imagining spiritual things.
There are studies that show Montessori students tend to have better executive function, better working memory, and no significant difference in creativity. I'm not aware of any that look at lifetime income or anything like that.
I'm not exactly sure, but measuring performance on education tests as a child is just a proxy for the whole point of education and raising children and it could even be backwards.
