Well I know this is late, but..
I think it can be taken as hypocritical. You said your son doesn't act like that..have you noticed the same things? Does he smoke cigarettes and steal your booze?
Honestly I'd agree with your perception that this boy is getting away with a bit too much. When I was 15 I didn't fully understand the love/caring that my parents were giving me...or how much I'd depend on that the rest of my life. Most 15 year olds don't realize this..
The first thing I thought when reading about the other boy bringing his stash down from his room with his pipe, was that if it were me and my parents let me go upstairs and bring down my stash to give, i'd give em a couple grams while I had an ounce or more upstairs...catch the drift?
You don't have to go all fascist on them, but you at least might want to watch him give you the stash? I'd say that's only smart.
For all she knows there's a ton of stuff up there with it. And most likely more than the bit he handed over.
Just two cents.