I think alot of what you mentioned is correct, if he had a mama & papa family upbringing .... papa would give him a clip under the ear for smoking, he would ban him from mixing with the pot head kids and he would make sure he attended school.
Not sure the 'friends' would really do it deliberately, I think it's just a hang out ... chill out type of thing and ' I don't care about school or anything ' attitude.
I think boredom causes alot of this, as when kids are bored they get into mischief. If they don't experience boredom as in ... play sports, go jogging, get a hobby or whatever .... then they don't have time for drugs or drug kids.