For a person to be the Imaam when he Teaches Mature Girls without Hijaab Print
SALAAH.. The Book of Prayer - Congregation and Imamah [leading the Salaah]

For a person to be the Imaam when he Teaches Mature Girls without Hijaab

Q: Salaah-738: What is the ruling concerning a person teaching Qur'aan to girls aged 15 and 16 who are not Mahram? Can salaah be performed with such a person as the Imaam?

Answer: It is wrong to teach girls who are of age and those close to this age when there is no Hijaab between them. Although one may teach them when the laws of Hijaab are practised and when one is not alone with any of them, it is still in the best interests of caution not to do so. It must be only a Mahram or another woman who should be teaching such girls. If a person does not exercise caution after knowing this ruling, it will be Makrooh to perform salaah behind him. And Allaah knows best what is most correct.

Fatawa Rahimiyyah vol.2