Legalizing and regulating marijuana is the only effective way to prevent underage children from getting it. When I was in high school, it was pretty much impossible to ever get alcohol, but it was easy to find weed any day. I still kept good grades and got a 2030 on my SAT in my senior year (and I smoked just about every day) but there are some kids who don't have their priorities straight like I did, so it is important that this temptation is kept out of their reach. For that reason I would advocate having a legal age of 21 to purchase and consume cannabis, and possibly an age of 18 to be able to grow your own (make the young adults appreciate it more :P). Also, in response to Rudy, your concern for people "getting hooked on it" is unfounded. According to a study published by the Lancelet, a prestigious British medical journal, that reviewed the addictive potential of close to 30 legal and illegal drugs, marijuana scored very low. Nicotine, caffeine, and alcohol are actually much more addictive. I have done lots of research now that I am attending the college of my choice and have access to the online databases of many peer-reviewed scientific journals, and have discovered that the most "healthy" way to consume cannabis is through vaporization. In this process, the plant matter is heated to a point where the chemicals are activated and release vapor, but no smoke is produced, and therefore all tar and carcinogenic matter is avoided. Edibles are another way to go to avoid smoke but I think eating cookies and brownies everyday may make a patient slightly rounder (especially if the patient is in a chronic debilitating condition and unable to exercise). Best of luck to everyone educating themselves and others and remember to keep an open mind and evaluate your sources critically!