So are you ok with four year olds in niquabs then, as happens at my son's school? Or burquas in the playground? I'm not allowed to come into the playground naked or wear my Stalin is Great T shirt. (At my school you'll likely get stoned for an Israel tourist t shirt) and my son has to wear a uniform. So how far do you go? Why is it ok for a woman to wear a burqa that signifies nothing good?
schools are very different places. in fact, it's so acceptable to tell children what to wear to school we do it daily. I have never seen a niqab in school and my local schools have plenty of muslims. But if you want to wear a Stalin is Great/Israel is great shirt, go right ahead. My guess is that no one will, or even can, stop you.
I in fact object to the niqab in public in general. That is asking for a high degree of exceptionalism. NO ONE else is allowed to cover their face, and I think there are compelling security reasons not to allow exceptions for this.
But, this doesn't counter anything I said, as children are not part of your body. I'd say we should allow children to wear a hijab, but not the burqa (if you are wondering wear I would draw the line). I'd say there is a good case that a child's education (social and academic) may be harmed with a niqab, but not a hijab (I do see many hijabs at local schools, and people seem to get along fine).
But, the french ban is a blanket one, and none of these arguments apply to sikh and jewish boys, who must abide by the school ban. Why are they having their rights restricted?