@freemo When an adult would be able to go to a public school, to study 1st grade material of their choosing (taught by a voluntary 2nd grader), without a hint of shame, I'll also be puzzled by stupidity.
Opportunity to study by yourself doesn't count without motivation, which primarily comes from the approval and support of your peers. These days I don't think "go back to primary school" is often said as anything but mockery, even by people who might not have mastered the material themselves.