Sudbury Valley schools do feature adult supervision I believe -- so if the goal is just to dump the kids somewhere while the parents work overtime, that model works fine.
As for whether external pressure is necessary to get kids to learn calculus or statistics, maybe. But I'd argue that there are forms of "pressure" that would better motivate kids to learn such topics apart from "my teacher wants me to learn this" or "I won't get into college without this".
For example, getting children interested in statistics isn't that tricky. Play games of chance. Poker is a pretty good introduction to some basic concepts in statistics. And if you don't want your kids gambling, there are board games. Or fantasy sports. Granted, games alone won't teach you everything there is to learn about stat, but it might get a lot of children interested in the overall topic enough to pick up a textbook and learn a topic of their own accord.
As for whether external pressure is necessary to get kids to learn calculus or statistics, maybe. But I'd argue that there are forms of "pressure" that would better motivate kids to learn such topics apart from "my teacher wants me to learn this" or "I won't get into college without this".
For example, getting children interested in statistics isn't that tricky. Play games of chance. Poker is a pretty good introduction to some basic concepts in statistics. And if you don't want your kids gambling, there are board games. Or fantasy sports. Granted, games alone won't teach you everything there is to learn about stat, but it might get a lot of children interested in the overall topic enough to pick up a textbook and learn a topic of their own accord.