During my first year at university I took a course in critical reasoning. It taught me much about logical fallacies, effective argumentation, preconceived notions, and so forth. It was my first real exposure to that type of thing and it felt like many doors had been opened in the way I thought about the world.
Many of my long-held beliefs up to that point came under real scrutiny for the first time, and since then I've been a great deal more careful in my convictions, and meticulous in deciding what those convictions are.
I'd say that that definitely changed my life for the better. I'd love to see a basic course in critical reasoning taught to all high-school seniors. Why not teach it at an even younger age? Because it's my belief that, up to a certain age, pupils should be unquestioning information sponges. Education would slow down quite a bit if every student critically evaluated and questioned everything they were taught, wouldn't it? This does mean that stricter regulations should be in place when it comes to what is taught, how it is taught, and who teaches it, and why it's so heinous when children are taught complete bullshit, taught incompetently, or both.