How to give classes to a mixed group of (teenage) boys and girls
Question

                I am a high school student who
      recently came to Toronto, Canada, I was in riyadh for 13 years and I am giving islamic
      halaqas in my high school to Muslim students.  Boys to my left and girls to my right,
      the question is: Is this ikhtilat ?? Mixing between boys and girls??  I am the MSA
      leader and not quite sure of this issue ,,,, Salam
Praise be to Allah.May Allaah reward you for your efforts in giving useful lessons to
    these Muslim students in your city, who are in the greatest need of learning about their
    religion in a land of kufr. Perhaps your background of having lived in Saudi Arabia will
    help you with this. I advise you to concentrate on teaching them about Tawheed and correct
    Islamic ‘aqeedah (belief), explaining how to do acts of worship from a Fiqh point of
    view, and teaching them the biographies of the Prophet 
 (peace and blessings of Allaah
    be upon him) and his Companions.
As for the matter which you raised in your question, letting boys and
    girls sit together facing one another in one halaqah is not free from dangers, as you
    know. I think that you feel the same way, which is what made you ask this question,
    especially when we expect that the hijaab of the girls where you live is incomplete and
    that the faces of some of them, at least, are uncovered in front of the boys. For this
    reason I suggest one of two things: either get the girls to sit behind the boys, wearing
    full hijaab, so that you don’t feel embarrassed when you face the group to give a
    lesson; or put up a barrier or screen between the boys and girls, such that they can still
    hear your voice, if the girls do not want to wear full hijaab. Then they can ask questions
    from behind the screen, so long as they are not soft in speech, or they can write
    questions on pieces of paper.
May Allaah help us and you to do good and to call people to His way and
    earn His pleasure. May Allaah bless our Prophet Muhammad.