Generally the top ‘tres grande ecoles’ are considered to be ENA, X (polytechnique), and HEC. ENS is also well represented. It’s not so different in France from the US ivy leagues, they have very powerful networks as well that are disproportionately represented in American business and government but in France they are even more powerful than in the US. I am a graduate of an american engineering university and a French tres grande ecole and I am american. The networks of the French tres grande ecoles are very strong. Also, because they are 100% merit admits and require a 2 year preparation program, there’s not the issue of affirmative action admits devaluing the programs. It’s very clubby and French people generally view going to one of the schools as being set for life with a French company or in business.
In my view ENA is as you say bread and butter bureaucrat with a few excpetions. X and HEC are at least more useful degrees where it’s not all about leaching off the public.
An interesting thing about France is how discriminatory they actually are. It’s prevalent but one interesting fact that illustrates the issue is how it’s a requirement to include a picture with your resume to make sure you aren’t an Arab or black. They government doesn’t collect demographic information (it’s illegal) and Americans tend to think that it’s because of some scheme so that people don’t realize how many muslims there are but it’s really so that no one has to admit that muslims and blacks live separate lives, in poverty, and don’t have social mobility. It’s really pretty shocking to look at French businesses from professionals to middle managers and up, it’s all white Frenchmen. There isn’t affirmative action like exists in the US. There’s nothing wrong with it and I prefer things to be on merits only not skin color. Similarly, outside the cities, it’s 100% conservative white Frenchmen. France isn’t quite the stereotype people think of.
I believe they do not write their names on exams so that the grader favors not the ethny.