Yes, that is absolutely the case. Every detail of the curriculum is decided by the Ministère de l'Éducation, as well as, for example, holiday dates.

Other matters can be negotiated between the Ministry and the town council, like the number of teachers or number of classes.

What a school can decide, maybe (and provided the mayor of the town where it is located, agrees), are super trivial matters like the timing of recess, etc.