You realise that alcohol is a drug, right? And you realise that alcohol is by far and away hundreds of times more harmful than marijuana, right?
Read up.
Of course I don't, here teachers boast all the time that drugs are bad, and basically expel any pupil who even does drugs, but when it comes to alcohol, all they do is give someone a slap on the wrist.
My point is that while people bring their drugs to school, the people at my school who drink alcohol keep it out of the school's business.