In school, our teachers would pull that trick all the time, and I think it usually worked. And let’s be honest, we would probably have made fun of our teachers if they confessed their ignorance about a certain subject. Kids can be jerks sometimes, especially when they’re in a pack. I know we were!
But the older you get, the more you respect the answer “I don’t know, I have to look that up first”. I guess that doesn’t come with age per se, but with the experience of how much you can’t remember yourself!