Wikipedia
The gwageo (or kwago) were the national civil service examinations under the Goryeo and Joseon dynasties of Korea. Typically quite demanding, these tests measured candidates' ability of writing composition and knowledge of the Chinese classics. The form of writing varied from literature to proposal on management of the state. Technical subjects was also tested to appoint expert on medicine, interpretation, accounting, law etc. These were the primary route for most people to achieve positions in the bureaucracy.
Based on the civil service examinations of imperial China, the gwageo first arose in Unified Silla, gained importance in Goryeo, and were the centerpiece of most education in the Joseon Dynasty. The tutelage provided at the hyanggyo, seowon, and Seonggyungwan was aimed primarily at preparing students for the gwageo and their subsequent career in government service. Under Joseon law, high office was closed to those who were not children of officials of the second full rank or higher, unless the candidate had passed the gwageo. Those who passed the higher literary examination came to monopolize all of the dynasty's high positions of state.