PARIS -- The phone message is one of 10 waiting for Sylvain Zenouda at the local office of the Jewish Community Council of greater Paris: A gang of 15 North African teenagers, some of them wielding broom handles, had invaded the grounds of a Jewish day school on Avenue de Flandre in northeast Paris the previous evening. They punched and kicked teachers and students, yelled epithets and set off firecrackers in the courtyard before fleeing. [...]