> This law is useless because schools can adequately set their own rules.

This is just a terrible argument. Just because a subset of people may be able to enact rules on their own does not mean you shouldn't create consistency at a higher level. Especially if you desire a specific outcome instead of having some groups come up with something completely different.

Also this law was one of Macron's campaign promises. People voted for this and people got what they voted for. Apparently people didn't want schools to make up their own rules.