And yes, there are gaps. I took Jack in for assessments when he was 4, and she asked him about skip-counting. Whoops. Forgot that one.
But I also have seen how quickly gaps are filled in when the situation comes up. Once he knew about skip-counting, he figured them out quickly. So many of the "learning goals" are filled in with one video, one class, one morning of watching PBS-Kids while I scramble to catch up on my teaching work.
I want to give my children that independence in learning earlier than age 20. Especially because it is working.
Jack attends Cosmic Kids Club at the Air and Space Center. And the others will too, when they're old enough.