My parish priest told me that the Catholic Superintendent of our local high school (town population: 5000) told him that there is a large number of students who describe themselves as "Wiccans" or "witches," and a smaller number that identify themselves as satanists.
I'm 39, attended a high school with 1,250 students, and don't recall a single self-described witch.
There is a phenomenon here to see for those with eyes.
But what fads were there, when you were in H.S.? I can't remember any witches in H.S. (I'm 35), but I remember a fair share of heavy metal fans and D&D players (with me occasionally among the latter) who came in for much the same thing. A few self-destructed; the majority when on to be adults in the same basic range as most adults.
OTOH, I noted more than a few self-described witches and the like, when I was a freshman at the University of Michigan in 1984. There were a pair of roommates, one of whom was fundamentalist Christian, the other a self-described "white witch." Generally they got along. But when the did argue they would start -- as one of them put it -- "furiously blessing each other."
Don't remember any from my high school, well maybe a few rhyming words. But when I was in 10th grade (I'm older than you BTW) a group of us got into ESP, and did some exploring into the occult. We went along with a lot of curiosity until one Halloween night when we held a seance. Coincidence or not (and I think not) some spooky things happened. It scared us silly. That spring several local churches experienced simultaneosly (and independently) a revival among the youth.
I worked with a summer youth program about five years ago. One of the students in the program said she was a "witch" - and had some pretty strange practices that disturbed her roommates. The next year my wife's then 16-year-old neice, pregnant at the time relates to my sister-in-law that she is a "wiccan." Both of these were pre Harry Potter.
My point is that kids are curious and they're seeking the meaning of life. I will grant you that a diet of Harry Potter along with the occult, goth, etc., etc. and nothing else to balance that is unhealthy and even dangerous.
But a major key is parental involvement. My son is well aware of our beliefs and is well aware that the Potter books are fantasy. Because he's read them now and clearly views them as what they are - make believe, I really believe there is a good chance he'll be less curious about the "real" occult later on.