As harmless as weed is, i'm still for waiting till your at least 16 to smoke. Or at least smoke seriously, an occasional toke when your younger is no problem. If you start actually falling behind in school, I would take it easy and get your prioirities in order. School is most important.

Theres also a level of maturity/mental health I believe the user has to have. Psychedelics can be a total mindfuck and defenatly isn't for the weak of mind. Just know whats going on, and no, demons arn't wispering in your ear when you hear voices and you wont be possessed. Just some examples of paranoia...