I'm not from the US, I'm from Israel. When I was a child swimming was part of our school curriculum, and I learned to swim at around 7 I guess (I already knew basic breast stroke my mom taught me at 4). But that was in a small community that had its own swimming pool, I'm not sure what's the norm in big cities that don't have many public pools. Also, the public education system here as been degraded quite substantially in the past 30 years.