How many of these kids have read what percentage of the books which are legitimately freely available? I've never encountered a kid (other than my own) who has

How many of these kids have read what percentage of the books which are legitimately freely available? I've never encountered a kid (other than my own) who has read: https://mathcs.clarku.edu/~djoyce/java/elements/elements.html https://mathcs.clarku.edu/~djoyce/java/elements/elements.htm... but have encountered many others who struggle with geometry.