Thank you SO much for the hilarious stories, everyone! It's incredibly reassuring to know that my son isn't the only one who's suddenly misplaced his brain, on reaching adolescence.
It's amazing how focussed he was last night, playing his new video game with his buddies...
Now, for me, the trick is going to be convincing my mother that the boy is normal.

She's never had anything to do with raising boys, and she keeps calling me to offer advice. Some of it is good, but I wish she'd understand that the real solution is just going to be time and maturity.