Rav Sternbuch has a teshuva 5:278 regarding the incident described before. It is part of a larger discussion about men teaching Torah in girls seminary.
At this point it is important to note that in recent times that kiruv (religious outreach) has become widespread. They have succeeded in bringing back many souls to the life of Torah. However it is often a mitzva habah b'aveira (a mitza associated with sin) because of the close association of teachers or rabbonim to the girls in private conversation. This brings many tragedies and causes chillul HaShem (profanation of G-d's name). (There have already been a number of cases that have come before us at the Bedatz concerning kiruv workers who deal with girls and women which have resulted in tragedy.)