Preschool can provide a boost, but the gains can fade surprisingly fast

Grade level schools, adopted in the USA in the middle of the 19th century, essentially dumb down those who are a bit more advanced at an early age. It takes a few grades to destroy the good work of parents preparing their preschoolers, but the playing field has pretty much been leveled by 3rd grade. :(

https://en.wikipedia.org/wiki/Prussian_education_system#USA

That's known to be true of Head Start.[1]

[1] http://www.edweek.org/ew/articles/2010/01/20/18report-b1.h29...

They mention this in the article.

I would also question if most of the primary education is useful. Some of it is useful, but not much of it for the number of years put into it.

Plus students who are good at an early age are dumbed down by this kind of education system.

Personally, only secondary education made any significant impact on my career.

I've seen this claim a lot, that smart students are 'dumbed down'. Is there any non-anecdotal evidence of this? How are you measuring intelligence and what is the reference point?

Just another example of the iron law of g immutability.