This is right out of scripture from the Religion of Pot. I have been hearing this nonsense going back almost a decade, and only the truly pious members of the church of the green weed believe nonsense such as this.
Who are these "Young People" who so report? Stoners? Not a good cross section of the available demographic if you ask me. Sure, Stoner teens can find weed because they've worked diligently to set up their supply lines.
Other kids? Not so much. Unless they know a stoner or something.
"This survey was conducted by telephone, utilizing a random-digit-dial technique (RDD), in which a pool of telephone numbers was created representing all 48 continental states in proportion to their population, using extensive information concerning telephone number assignments across the country. The random generation of telephone numbers has the advantage of capturing unlisted numbers. This pool of randomly generated telephone numbers was prepared by Survey Sampling, Inc. of Connecticut.
"The random-digit telephone numbers were called, and the household was qualified for participation in the survey by determining that a teen 12- to 17-years old lived in the household (see Appendix C for screening questions). At least four call back attempts were made to each telephone number before the telephone number was rejected."
http://www.casacolumbia.org/download/file/fid/640