It was a Home Ec class in junior high. (7th grade had both Home Ec and Shop, 8th grade you picked one). We had just finished "how to order from a catalog" (because I'm old) and the teacher passed out magazines and we were to find an ad, then list 5 ways it was deceptive.
The first few were easy. Showing money, attractive people, fast cars, happiness...but then things got subtle.
Once we did, we shared with the class. I don't recall my ad. I DO recall the lesson that clicked for me. It was an ad for Bayer aspirin. "4 out of 5 doctors recommend", the ad said, something I had seen on countless commercials. "Who picks the doctors?" asked the student.
Blam. Mind Blown. I had never considered that particular aspect. This opened up that "clinical studies prove..." doesn't mean anything. Awards, certifications...the idea that I could be told words that were technically true but misleading went from something that could be told to me and that I could recite back to something REAL, that I applied on my own.
I don't know that you can teach critical thinking, but I know that you can push opportunities for it to 'click'. This was one day of one class out of thousands of days of schooling. I learned lots of lessons in school, both factual and personal, and while there were likely many other more subtle lessons about critical thinking, this was a real moment of change for me, and it feels like it could have so easily slipped by.
We should absolutely push students to be ready to accept evidence while also questioning what is presented. Repeatedly. over and over again, because you never know how many times it will take to suddenly start working.