The only people complaining about the system are either those that know how it works but failed to get in

Heh. But this implies, doesn't it, that it is by nature an elitist system? That is, there are large numbers of people not complaining, because they have no notion of how it works? For them all this is Mandarin, it might as well be going on in the Forbidden City.

The truth is that classes prépa/Grandes Ecoles form an efficient socio-economic filter. In almost all cases, the family (and its background) will decide that their child will (if capable, I agree) enter this system. In almost all cases, access to a good lycée is necessary, and the good lycées are for the upper stretches of the class structure. Detailed knowledge of an intricate system is necessary, and considerable expense of time and energy to work it. (This is why teachers' children may get in, as representatives of the lower middle class, because their parents are in a position to learn the rules of the game and push their kids in the right direction at every twist and turn).

This isn't a sour grapes reaction on my part. I went through the elitist system of another country, and my critique is simply the result of my observation of what happens in the French one.