Complex sentence: By contrast, to be admitted into one of the French "grandes écoles", most students study in a two-year preparatory program in one of the CPGE before taking a highly competitive national exam.
Split into simpler sentences: By contrast, the admission into one of the French "grandes écoles" has to be earned. The "voie royake" (litterally royal road) is the CPGE: a two-year preparatory program before taking a highly competitive national exam.