So if the sex's were reversed and you were girl, the guy would have been a sexual predator and should be imprisoned?
No. I don't think that a seven year age difference, especially when the younger party is so close to 18, constitutes sexual predation.
As I said, it's a lapse of judgment in the extreme, and jobs should be lost and teaching certificates revoked, but there's no "victim" here - unless of course the person in authority used her authority in a coercive manner. Then that's a completely other circumstance.