Teenagers are obviously different than small kids, but this seems to be a more systematic problem than not failing small kids when they start school. Litteracy is only 99% in France in the 15 and older group, on par with the USA. I think that we can agree on the US system being broken. Looks like France is following suit. Given that, fixing the school system in France and learning from Finland does not sound like a bad idea.
Literacy rate does not mean anything - the criteria is too low to account for the fact that most kids do not understand the words well nor master their own native language and obviously have a very hard time writing correct sentences on their own. It's not just about making kids fail indeed, but that's one factor that goes with everything else, i.e. evaluating the students less and less and making the programs lighter and lighter in order to accommodate the dropping overall level of students.
I feel we are gettinf further and further away from the original discussion and moving the goalposts as we go along, but the key takeaway from this is that France should focus more on supporting weaker learners rather than just administer more and more tests with strict passing grades.
A failing grade is pretty useless to all parties involved unless it is used to assess and correct what the underlying problem is.
Unless you have a better idea?