I am not sure

My kid goes to Challenger in CA. When he sang 50 states in grade-K, we were very pleased too. But he forgot that song after 3 months when he moved to other topics. It's hard to evaulate the long-term impact of the early learning. But one thing for sure: if you want to teach your kids, their ability to absorb is huge. For how long the knowledge will stay in their minds? I don't know.