An exchange to France is possible throughout the year except the days in blue mentioned in the calendar.
Not all the schools of France have their holidays at the same time. The country is divided in 3 zones: A, B and C. Each zone will take its holidays per turn. Except Summer, Christmas and "All saints" holidays.
When the schools are closed, they are really closed and no contact with the families/students/teachers/principal can be done.
An exchange in September has to be confirmed, by the participant, before the 5th of June to give enough time to the French school to be ready for September when the school reopens.