It sounds as if the problem is not just the creepy teacher but being alone with the teacher, right? She would be well within her rights to ask (politely demand) that the school insure a safe learning environment, aka NEVER being alone with him. Have her make her request in writing, thus establishing a paper trail.
Then, she needs to document all the time in that class as it happens. The first time that there isn’t a witness to her interaction with that teacher, she should take it up with first the school administration, then the locall media.
Usually when the school is approached like that, they cave. No one wants a lawsuit and since by that time there would be documentation, the school would lose.
My husband is a teacher. He makes it a point to never be alone with any student. The possibilities of accusation are just too great.
That’s one thing I first thought. Why would this teacher want to be alone with his students, when there’s always the chance of an untrue accusation?
It will scare the crap out of him.