The Calendrier Scolaire points out the different dates for holidays amongst the different educational zones in France.
The three distinct zones when it comes to the dates of when classes break up are:
Caen, Clermont-Ferrand, Grenoble, Lyon, Montpellier, Nancy-Metz, Nantes, Rennes, Toulouse
Aix-Marseille, Amiens, Besançon, Dijon, Lille, Limoges, Nice, Orléans-Tours, Poitiers, Reims, Rouen, Strasbourg
Bordeaux, Créteil, Paris, Versailles
The aim is to stagger French school holiday dates so that the roads and public services are not inundated with people.
Also you'll find just to the right of the page there is a link to a printable version of the calendar, as well as the opportunity to download the dates in the iCalendar format.