Plain Jayne by Beth Kean

A teenage prank leads to a crazy new life for Danny Wise. Trapped by his schoolmates, he finds himself carried from the shower and tied in the girls changing rooms and forced to await their arrival, and that's exactly what happens until Jayne races to his rescue, Plain Jayne, the butt of every joke. But Danny finds her glances intoxicating, so much so that he finds himself driven to show her again.