The one thing I wish I’d been taught in high school, above everything else, is critical thinking. Entering college, I lacked a good many skills I feel I should have had, but the most embarrassing was the skill set to tell a good argument form a bad one. My bullshit detector was very, very poorly calibrated. I wasn’t alone, and my ethics professor exploited this mercilessly to his apparently endless amusement.
A course in formal logic is probably too much to expect of high schools. Fortunately, there’s another option. Ali Almossawi has written a delightful book entitled An illustrated book of Bad Arguments. It’s a marvelously accessible catalog of logical fallacies complete with easily-understood examples.
The book can be read online and I strongly urge you to do so and share it if you like it. The ability to tell truth from crap isn’t nearly as ingrained as we’d like to believe and books like this are a terrific tool to hone our skills.