Kids enter school at 5 or 6 with a range of reading abilities - some can recognise simple words, but very few are fully literate. The UK currently has a literacy rate of 99% -- something is going right.

Learning to write and perform basic maths doesn't seem that hard to us, but for most of human history was the reserve of a select few. Perhaps the fact that it seems so easy is actually because school can be quite effective at times?

No fundamental changes to learning are required when you push literacy rates from 10% to 99%, it is simply a matter of including more people into the learning process of a few years that existed for several millenia. If kids had a retention rate of at least 10% after 11 years of schooling and “are you smarter than a 5th grader” couldn’t be a thing, now that would be impressive.