Answered by Shaykh Faraz Rabbani
1) Would it be permissible for a menstruating woman who teaches in an Islamic School/Sunday School to teach if the class takes place in a designated classroom within the mosque (not inside the musallah)?
2) Same question regarding a menstruating woman who goes to the mosque regularly for Arabic/Tajweed classes?
Walaikum assalam,
This would depend how the mosque was designated when it was laid-out. In most multi-purpose mosques, it is only the prayer area that is designated as a mosque, and the classrooms and other facilities are not part of the mosque. If this is the case, then a menstruating woman may enter such areas, though not the prayer area, because of the clear hadiths prohibiting this.
The same ruling would apply to the classes you asked about.
Wassalam,