10 years but the 4 years of studying there are included in the 10 years. Most continue with a PhD (at least 3 years in France).
And then it is allowed to do research abroad, not for the French governement, for instance in an US university. Working for a private company entails to have to give back just part of the money.
And there are 4 ENS (écoles normales supérieures) in France so even more opportunities!
And there are 4 ENS (écoles normales supérieures) in France so even more opportunities!