Its your girlfriend/s or a frenemy perhaps. A group of boys will not find any pleasure in sneering and sniggling behind your back. Not a teacher for sure - am i correct in presuming this person is always making reference to the particularities of the class to prove their presence there? This is why you say the messages are from different classes and from different people but you think its the same person because the narrative is always the same. Its all lies to to lead you astray. Which one of your girlfriends friends shows particular interest in this situation? Who has been subtly influencing you to believe the lie either by listening or by advising? Pretty Little Liars