dksbook: If you were sending your son to NYC, you'll probably recommend him to avoid the Bronx neighborhood, or South Central in LA, or... (you get the idea).

Same thing here: car burnings and other arsons happen in very specific areas: low income housing projects outside of the main cities (mostly concentrated around Paris), the "outer cities" so to speak, that are far away from the main touristic places or urban centers.

Total number of fatalities so far: I haven't checked the exact number, but probably less than 5 (including the two kids who were electrocuted in a power substation). The arsonists avoid confrontation and hide from the police. Their goal is to make the headlines on TV (and boy, does it work well..), their 15 minutes of fame every day. This is the "Reality TV" generation.

The other 99% of French territory is just going about their business.

Your son will be safe in Lille, at least much safer than in most large US cities, and if he's been there all summer, he already knows where to go and not to go.

BTW: I can't locate any travel advisory for France. The State Department "Current Travel Warnings" mentions the usual countries, the only European one being Bosnia-Herzegovina.