bob sleigh wrote:They were category B schools located below the grandes écoles.
Your reasoning is flawed by the fact that you assume that the preparatory and DEUG program in those years was fundamentally different, which is wrong.
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These two programs were different, especially for the expected level, the DEUG being more easily accessible. The idea that sup / spé would be as easy as the DEUG, what a funny idea!
Grandes écoles and INSA were intended to train engineers, universities rather researchers or executives from the public or private sector. And sup / spé was intended to train for entrance exams to major schools, the bar is much higher. Not the same job, not the same training.
(This is from experience I'm talking about).