I come out of a top 5 Grande École after having done my classes préparatoires in the highly famous high school of Boulogne s/s Mer and stemming from a family a tad above poverty; so I know a little bit what I'm talking about.
As I mentioned, it's highly correlated with students socio-economical status; now at least it's not conditioned on your grandparents stuffing an Ivy League with money, with your parents having time and money to send you on tons of extra-curricular, your family having been at Eton for centuries, or your father being an oligarch and sending you to Switzerland at 18 y.o.
You can spit on and scorn us and our system all you want (it's quite in fashion on the Internet, I'm sure you'll get a lot of upvotes for it), but at least it tries; and in my experience, it's the best one with the ex-soviet ones to balance high quality education with meritocracy.
> As usual in France, there is one rule for the plebeian and another one for the ruling class.
Sure, that's so typically French. It's true that Eton, Princeton and Beijing University frequently display students coming from the most remote and poorer part of their country.