@cats -- I hear you about concerns that kids will not get the guidance that they need at higher levels of a subject. The answer that we have gotten from the Sudbury school was that: (1) with the Internet, all information is accessible; (2) a staff member can help facilitate #1, if necessary; and (3) if #1 and #2 fail, the student can potentially gather up other students to vote for (everything is democratic -- "teachers" (they don't really call them that) get the same one vote as students). Overall, their answer to all of these sorts of questions is, if someone wants it enough, they will find a way and the school looks to facilitate that.
@BrandNewPapa -- Interestingly, my daughter has a strong interest in art. But she is eight and lots of kids like art when they are younger only to grow out of it later. I would hate for her to not get enough exposure (even forced exposure) to try something new so as to see if she likes it.
@formerlydivorcedmom -- I share your concern about not getting enough exposure to other areas than their, at that time, predominant interest. The Sudbury school would say that kids are inquisitive by nature and by mixing ages and mixing kids with all different interests, they'll pick it up, either directly or indirectly (indirectly could be playing Minecraft or somne other video game). And if they didn't, they didn't need it. I'm not saying that is valid, just that I can't answer if it is true or not. I'd need to have enough faith in their system and then let it work.
On the SAT question -- now you hit on it, something quantifiable that I can compare to! -- well, it doesn't seem like there are hard numbers out there. Nor do they seem to keep traditional records of X number of kids went to a 4-year school, of them A went to a top 20 school, etc. Of statistics I could find, the number thrown around is that, supposedly, 80% of Sudbury kids go on to college, but they don't always do it immediately after K-12 and they seem to often go to a two-year/community college first. On the latter, it sounds like a lot of kids start taking some classes at community colleges a year or two before graduation to get a feel for what post-Sudbury school might be like. They report that must kids excel at those classes. They can then use these classes and the transcript for the community college to provide 4-year schools something to prove their abilities. Some do study for and take the SAT/ACT and claim they do just fine -- learning to the test and knowing fully why they are learning it -- but, again, there are no hard scores.
It is, of course, really hard to deconstruct exactly what went into our successes and failures. With that said, when I think back on my own childhood, probably the things that taught me the most were the activities that I was passionate (back then they described this more as obsession) about. These were largely things outside of school because school can expose you to something but then you move on to the next thing. Anyway, I'd say my love of computers, and infinite hours spent on a VIC-20 and Commodore 64 "importing" games, programming, setting up a BBS, talking with people all over the World, has probably served me better than anything else.
For those that are interested, here is a study based on a survey of unschooled students. The results were overwhelmingly positive, but even the author admits that might be because only those with positive experiences responded:
https://www.psychologytoday.com/blog/freedom-learn/201406/survey-grown-unschoolers-i-overview-findings This school allows kids (actually requires kids if they want to attend) to put in a week at the school. I'm slowly moving towards letting my daughter at least try that to see if it works for her.