* The name is slightly different: There might be a similar-sounding name, or a misspelling. Could you be thinking of a different name?
* It's a small, private school: Many small private high schools aren't as well-known online.
* It's a fictional school: The name might be from a book, movie, or TV show.
If you can provide more details (location, state, anything else you remember about it), I might be able to help you find it.