When I'd sit with my buddy and his family, in church, I'd barely notice his kids. BUT... he was very aware of them. They'd be getting a little to...whatever... and he would just lean forward and make eye contact and then sit back. The offending kids instantly stopped, whatever it was they had been doing.
Something I had barely noticed.
Oh... my buddy has 10 kids.
(Actually, it was his wife who HAD the kids. He was just there to "pitch" in the first inning and "catch" in the ninth :)
Yes, that is what happens with a child when he has been properly taught to behave. They will get squirmy, and that is quite normal,but they need to be reminded the way your friend does it.
I know about big families, as I was raised as one of 9 children. And my parents always received compliments regarding our behavior.