The main social functions of school seem to be to help students show off their smarts, conformity, and conscientiousness. Schools also babysit, socialize, and indoctrinate. But run my experience the two stated functions that school fans tout most often are (A) teaching students particular useful facts and theories,  and(B) teaching students how to think for themselves. 

When teaching students to think for themselves, it is not enough to just assign though-provoking essays or stories; students at some point must practice generating, supporting, and debating their opinions on particular example topics. And it doesn’t work to use topics with obvious agreed-on answers, like “is the sky blue?” No, to practice thinking for themselves, students need to engage topics where plausible arguments and evidence can be found on at least two sides. 

One standard set of example topics is offered by philosophy, topics such as free will, determinism, infinity, solipsism, or nihilism. But these topics tend to be pretty far from the interests and experiences of most students. Students are much more easily and usefully engaged on topics that are currently considered “controversial” in their world. But most schools are quite reluctant to let their students debate most such topics. Why?

When people listen to a debate on a topic, their opinions consistently tend to move toward the middle of the range of possible opinions on that topic. Thus increasing public attention to a topic is a reliable way to influence public opinion on it. And thus the eagerness of authorities to allow student attention on a topic depends greatly on whether this predictable movement is or is not in their favored direction.

For example, fans of intelligent design push schools to “teach the controversy”, while its opponents want the topic ignored. Vaccine skeptics would love students to consider vaccine skepticism, while the usual elites would not. And progressive teachers happily encourage students to discuss progressive proposals currently unpopular with most citizens, such as race reparations, universal basic income, or a wealth tax. 

Thus schools that are responsive to parents, politicians, or academic elites mostly do not allow students to debate topics where such powers dislike middle positions there, relative to status quo opinions. But most “controversial” topics are exactly of this form; some existing confident position, like “vaccines are safe”, is challenged by some contrarians, who win even if audiences only move to middle positions of uncertainty.

Thus while school fans claim that an important function of school is to help students learn to “think for themselves”, school authorities mostly won’t let students practice such thinking on the controversial topics most suitable for such practice. Me, I’d be happy to use public polls or votes to select the topics students are allowed to engage in public schools. But I expect that most public school authorities, including most teachers, would strongly opposed such a proposal.

Added 5Dec: Yes, there’s a decent case for the view that schools mostly select for skills, rather than actually improving them. Even so, thinking for yourself seems one of those skills that schools should be selecting for, even if they don’t improve them.