... OK, so how long before, out of consideration for other cultures, they're required to wear a headscarf. Some of their teachers with an immigrant background no doubt find women's hair to be distracting, too.

In fact, why no go the whole hog and mandate the niqab for all girls in the school?

Given their stated reason, there is no justification for holding back, is there?

While they're at it, it's probably very offensive to those immigrant-background teachers to be surrounded by infidels. Forced conversions are authentically Muslim; I think the school knows what it has to do.