Radicalism is no longer taught only in college; many younger students are getting a head start. Schools traditionally emphasized the “three Rs” – reading, ’riting and ’rithmetic. Recently a “fourth R” seems to have entered the American schoolhouse: radicalism. “When you go into a class where you’re supposed to learn about government or geography,” high-school junior Sean Allen says, “you expect to learn what the truth is.” He found out last year that some teachers don’t share his expectation. An Accelerated World Geography class at Overland High School in suburban Denver featured diatribes against the United States, capitalism and President...