I was a similar case as your older nephew. I couldn't sit still in elementary school, and teachers would bring up that I fidgeted a lot to my parents. At some point the school wanted to put me on meds. My parents told them to fuck off. As I grew older and classes began teaching things I didn't already know or couldn't grasp instantly (and was interested in learning) I was fairly calm and attentive.

I am forever thankful that my parents saw sense that I was probably just bored in school and were adamantly against the idea of fucking me up with meds.