I would argue that the 11s don't really count, since knowing them is trivial. The only one that really requires memory is 11x11, and it's probably not strictly

I would argue that the 11s don't really count, since knowing them is trivial. The only one that really requires memory is 11x11, and it's probably not strictly worth knowing, but then kids get the accomplishment of knowing a whole extra row essentially for free. I agree that the 12s aren't worth memorizing though. They're pretty easy to mentally calculate, being a combination of 1 and 2, and after doing that for a few years, the memorization will often happen naturally. No real need to force it.