Higher-class parents tend to be trimmer and have trimmer kids. It is not unreasonable to expect they have higher IQ’s and better memories as well. On the other hand, exercise is being shown to improve function among the elderly and now regular adults as well, so it is not unreasonable to expect that it might boost the brains of children too.
I agree with you. Could it be that the fitter kids have more involved parents that take better care of them, which usually includes seeing to their education as well?
Liberals will never admit that parents matter.
And yes, exercise is beneficial to people of all ages!