Not to mention the importance of the face itself and its expressions to children's emotional development. They look to their caretakers' faces for guidance in how to react emotionally to events: is she happy, afraid, anxious, angry, puzzled, sad, etc...

But that's besides the point. Women who wear the niqab only wear it in from of unrelated men, not other women, or children. They do not wear it in their own families, with related men, where they do want social relationships.

So they would take it off in class, but put it on if a man walks in, or when taking kids for a walk outside, etc. So dealing with fathers, male teachers or principals, the janitor, etc., on, off, on, off....