Is this actually legit full true? It might be less of a gradient than other places, but in our two years in Norway our children went to two different public schools which were in immediately adjacent suburbs - both good locations, and there was a definite difference in the management of the schools which was visible through all our interactions with them.
The second school was clearly better in our experience, despite being part of the same system.
Norway isn't "EU" for those purposes, but I suspect it's similar. The same way that different hire car offices or different pizza parlours in the same "chain" can have quite different quality despite theoretically operating under the same policies.
(edited to add)
While these things, in theory, normalise out over time as staffing changes in individual schools or individual franchisees - your kids are often only at each school for a handful of years, so there'll definitely be some attempt to find the better ones based on what you hear from parents of kids a year or two ahead... and those with enough money to just move house into the "best" zone will still get their kids into the better school.