I'm an English teacher in a lycee in southern France and understand your frustration. I work for a private association that hires native English speakers to teach English and History/Geography within the French school system and alongside French Education teachers. When I started my job, I was surprised to learn that when a teacher is absent, there are no substitutes to take over. For us, if another employed teacher can and is willing to take the class, then that is what happens. Work is provided. If not, the class is canceled. For a medical issue that I had last year, I found out that one of my classes didn't meet for two weeks! Luckily, I was able to connect with most of the students through a Facebook page that was created to let students know about homework, upcoming tests, teacher absences, special reminders, etc.
Currently, I am on maternity leave (I go back after the February vacation), but you can bet that I'm checking in with the replacement teacher and making sure that I know what has been taught, what I will encounter upon my return, and so forth. Obviously, it was a planned absence, so my position was advertised and the teacher is highly qualified. Our association is growing too, so it sounds as if we may be able to keep a couple trained teachers as substitutes. With the amount of teachers we have, the one or two hired should have more or less a full work week, especially during the winter months.
Unfortunately, it doesn't seem like this is important in the French Education system. The French Education teachers that I know DO care about their students (of course, there are some that I know who don't) and they prepare lessons like crazy and correct essays and try to have lessons that are creative, fun, and educational, but for the ones that are there who don't seem to care, I wonder about burnout. Perhaps they came into teaching with great enthusiasm, but looking at the things that they are asked to do and then looking at what they get paid which, in my opinion, is horribly low considering everything that they are asked to do...it's enough to get anyone down.