> Base 20 is not a popular notation for numbers […] We shouldn't make it harder for these kids
So much of what you object to is that something they’ve found more intuitive and engaging isn’t what unintuitive disengaging stuff they’ll encounter. But developing intuition for math is far more valuable than developing conformance to how it’s supposed to be done. Who cares if that intuition is developed with some idiosyncrasy from what you consider normal? The math is math, the principles are consistent, the knowledge is transferable. Insisting they learn the same things a different way is totally arbitrary and counterproductive.