I don't have the numbers right now, but one of the big pushes for reading science right now is that there is a gap between the kids who very well could pick up reading on their own and those that need the letters and sounds taught. The latter number is concerningly huge.
So while it might sound nice to expose kids and hope they're in the former group, it's not trusty.
It's impossible to say why those teens can't read, but I feel a parent ought to know when one reading education plan isn't working.
On the other end of the spectrum, today zi l has to assure a mother her kid was reading at an age-appropriate skill level, was passing all assessments of such, and no, is not at risk of having to repeat kindergarten.