Fuck that dude. Are there cameras or witnesses? I know you said you're not trying to get him in trouble, but you need to report this again or follow up with that teacher. If he's 18, he is considered an adult and you can definitely press criminal charges. If the school isn't doing anything, either ask your parents to contact the school and really explain the situation, or try and find a teacher that you truly think is good and looking out for students.