From what I have seen, half the students in my science class end up high (after lunch) but can still concentrate.
But last semester, their was one individual, who drank alcohol, and couldn't pay attention in class because they were sober. Complaining to me saying "Can you read this to me, I'm sober".... Not surprising seeing as this person looked like they were all tired out drinking, but that they don't seem to keep this information to themself, as I didn't really care, so I moved my seat away, seeing as, this would cause a distractiong to me and for this person.
I don't know why some teenagers parents allow them to drink, but from what I have heard, that, they sneak alcohol from home, and drink it after school, or do it at home when their parents are gone or asleep..
And as usual, I get asked "Do you drink? You want to try some?"