Maybe the story is about cocaine use well after high school, or something like that he actually sold or shared the drug to and with others while in high school or even after.
Hard to imagine that a high school cocaine user would just go cold turkey upon graduation. He kept smoking cigarettes, and probably has used coffee his entire life, so he likes stimulants. If someone gets to ask him a question at a town hall or press conference see if he ever sold or widely shared his coke “stash”, especially with other youngsters.
I used to do a lot of coke in high school—when I could afford it. It was expensive, so that wasn’t very often. I quit after high school because I had a job, and needed to function at a much higher level. Random drug testing also factored in there somewhere. Never did it again. Never really missed it. I do drink coffee and a Red Bull every once in a while though.