Following a man who Teaches Girls who are of Age or Close to it

Q: Salaah-403: What is the ruling concerning a man who has been teaching non-Mahram girls who are of age for the past fifteen to sixteen years? Can salaah be performed behind him?

Answer: It is wrong to teach girls who are of age or close to it without them being veiled from one. Although it is allowed when they are veiled and when he is not alone with them, it is best to avoid it. A woman or a Mahram should be teaching them. When a person does not take the necessary precautions despite knowing the ruling, it will be Makrooh for him to be the Imaam. And Allaah knows best what is most correct.

Fatawa Rahimiyyah vol.2