I think the rise in school expulsions is more telling. "In the 2008-09 school year, before Colorado's boom in medical-marijuana dispensaries, 534 students were expelled for drug violations, according to state Education Department data. In the 2010-11 school year, that number was 767." Correlation is not causation, but I can't attribute the increase to any policy change in the schools. Anecdotally, I'd say almost all of the expulsions are for medical marijuana.