Not an issue of ethnic diversity, but rather divisive religious fervor
The French have the correct answer to religious fanatics who desire to brazenly display religious garb in a properly secular school. It's divisive, contrary to the enlightened secular values of the Republic, and it is rightfully forbidden. Of course, America having only evolved to a much lower level of social advancement, and much more backwards and primitive than France in such respects, is still far from such intellectual illumination, and still tolerates and in fact rewards the ignorant devotion of the unlearned masses, and the divisive practice of the mindless religious zealots.