Alot of people before they smoke say I won't rely on other peoples stuff. You most likely think that it has other drugs in it because D.A.R.E. tells you that but honestly I have never came acrosss any weed that was laced and its highly unlikely that a dealer would lace your weed because with most drugs that are physically addicting it would be unprofitable.
I am in a school with a zero tolerance policy aswell but teachers have never noticed me when I'm high in class even if you do geek out you most likely won't get caught unless you reek. But thats what axe is for.