One of those inconvenient facts: kids who will be successful in life learn to read at home before starting formal schooling, and they have an adult who reads with them three or more times a week; kids who don't get that at home are much more likely to remain illiterate or to read at well below their grade level. It's inconvenient because there isn't anything anyone except the parent(s) can do about it, and the parent has already made that choice by the time the kid gets to school.

This seems to vary quite a bit across countries which suggests to me that something can be done about it - I cannot say what though.

Parents can be encouraged and informed, to an extent, but the problem is that if they do not enjoy reading, you cannot pass on something you do not have yourself.

Another problem in the UK is that I think policy makers think of reading as a life skill, and education in general as preparation for work, rather than as something to enjoy - at least for the hoi polloi (or "the gammon" to use a disturbingly common term), their own kids are different.

There's not a specific age where this work has to happen. Reading a variety of challenging books aloud to the class is one of the best things schoolteachers (especially early grades) can do for their students. Listening/language comprehension is incredibly important and underemphasized throughout most schooling.

Reading per se (i.e. decoding written symbols into sounds/words, at least in English or similar languages) is a quite discrete skill that takes something like 6–12 months to learn to basic proficiency, working an average of, say, 15 minutes per day with direct guidance. It has some basic pre-requisites (attention span, interest, recognizing the alphabet), but can be done at any age; some kids might be willing to learn to read at age 3 or 4, but it can certainly be started at age 8, 12, 20, or 45.

After that, speed and fluency improves with additional practice. Like anything, it's easier to get very fluent if people start younger because they have fewer other obligations. Someone who learned to read at age 4 and then spent hours reading for fun every day for 10 years is going to be far ahead of someone who learned a bit starting at age 8 but never had much help, and afterward only occasionally skimmed some magazines for the next 5 or 6 years but mostly spent their time on something else.

> kids who will be successful in life learn to read at home before starting formal schooling

What I did read was that early reading is not important to anything of importance, at best it can be a proxy to filter out neglected kids. Whether the kid can learn at that point is a question of brain development and you as a parent wont achieve nothing by trying to force it.