You can't just start from the assumption that society would be more rational if rationality was taught at school. You'd also need evidence that rationality can be taught to a lot of average people. I don't think such evidence exists. Whatever taken out from the curriculum might be replaced by something completely ineffective.

Can't specific rationality techniques be effectively taught to a large amount of average people, though? I vaguely recall that there might be some examples of that in studies where the researchers taught participants a trick or two before submitting them a test of some sort, but my ability to recall specific examples is almost geometrically inverse to gwern's, so that certainly takes out of my point.