TV Show-Paranormal High School early 2000s

(i think these are the details but i’m not entirely sure) So when I was a kid I watched this tv show about a group of teenagers at a high school finding a book and it was some demonic type magical book. there was also three men outside the high school at their car that would help the teenagers solve whatever mysteries were going on. but they never left that spot. at the end of the show it’s shown they are actually ghosts from the 70s and were the first to find the demonic book.