Still, in France it means something different. For example, here's what I found about L'Ecole Polytechnique (english pages: http://www.polytechnique.edu):
Founded in 1794, the Ecole Polytechnique, a state supported institution of higher education and research, is the most prestigious engineering Grande Ecole in France. The Ecole trains the scientific, industrial and economic elite of the nation.
~ Exceptional scientists, many of whose names are now attached to fundamental laws and concepts, have walked its halls as students or professors over the last two centuries.
The higher education system in France comprises universities and other institutions called the 'Grandes Écoles'. The Grandes Écoles are the main channel for education in Engineering, Management and certain scientific fields such as life sciences. Entry into a "Grande Ecole" is not achieved the same way as into other higher education institutions. They recruit students in a very selective manner at a national level. It involves the passing through one of the 200 preparatory courses lasting at least two years after successfully passing the baccalaureat. The exam is very selective, from the top "Grande Ecole" (Ecole Polytechnique being ranked first), with more than 10 candidates for each place and going to more professional ones. The entry competition exam comprises written and oral tests on scientific and humanities matters. The vast majority of chief executives in France's large firms are graduates of the Grandes Écoles.