In principle, the religious clothing laws are wrong. I taught in a high school in France last year, and some of my students refused to go to school without the headscarf - I taught them outside.
In practice, it is often a necessary rule. A lot of converting to Islam does go on in France. The political situation there is very complicated. They allowed lots of Muslim Algerians and Moroccans in to help build up the country in the 60s, and housed them in purpose-built accomodation out of town, like in ghettos called 'cite [with an accent on the e that I can't get to show up here]'. Unfortunately the financial/social position of these people has not improved over a generation. There is tremendous violence in these areas, cars and schools are put on fire and burnt, there are stabbings... the French have done a terrible thing by not helping these people integrate into society. On the whole, many Muslims refusing to attend school because of the headscarf restriction come from these areas. It's a political, anti-French, as well as religious statement that these people make, against the French authorities. My experience of France, though I love it, has shown me it is quite a racist country. These kids would suffer attending school with the headscarf. Rightly or wrongly, they'd be associated with the violence. There would be arguments. There already are. I had a hard time controlling a class of kids arguing about Islam and Judaism and getting incredibly offensive. You might answer that brushing the problem under the carpet isn't a solution. In theory, no, in practice it makes working life much more pleasant for teachers and students. They come to the classroom without politics and learn on an equal setting.
Another point to make is that the French claim (whether this is true or not I cannot tell you) that many families force their daughters to wear the headscarf, so they want to create a neutral space for people to learn where they can 'get away', so to speak. Again, how true this is I don't know.
It's far more complicated than I've explained, but I don't think it's a bad thing. I'm Jewish, and take my religion seriously, but I don't think it's necessary for people to show their religion outwardly - it's a personal thing that should not be imposed on others. I don't see why it should be outwardly expressed, not in Judaism where for orthodox people it's supposedly compulsory, or for Muslims for whom, apparently, it's choice.
Some things are better left at home, if only for security reasons.