You may be right and Carry's kids may be geniuses. On the other hand, they may just be rising to meet the higher expectations placed upon them. In other countries Calculus is taught much younger than here in the U.S. and kids don't seem to have a problem with it on average.
In our schools we spend a lot of time talking about what the kids can't be expected to do, while in other schools (and home schools) they spend their time doing it.
Shalom.