I agree with this position, and wish we could do more of that in the classroom. However, the system we have defines the level of success a school has based upon multiple choice tests.
Honestly, after thinking this through so many times.... I no longer want see more taught in the classroom. How can a 7 year old child grasp the concepts and ideals behind the facets of history? We shouldn't worry about teaching history before puberty and even then, just the basics. Geography, sure, culture, sure, law, absolutely. But memorizing dates and events that have little or no significant meaning to someone at the phase of their life where Nickelodeon is trapped between their ears, and sugar is the greatest thing on earth? It becomes mere trivia.
I would only hope that by strategically depriving a kid at school, would promote them to ask more questions at home, and when they do independent research. At that point, is when you get that thirst for knowledge. Once that gets going, nothing stops you from understanding the universe that we live in.