After the collapse of the Han dynasty, the Taixue was reduced to just 19 teaching positions and 1,000 students but climbed back to 7,000 students under the Jin dynasty (266–420). After the nine rank system was introduced, a "Directorate of Education" ("Guozijian") was created for persons rank five and above, effectively making it the educational institution for nobles, while the Taixue was relegated to teaching commoners. Over the next two centuries, the Guozijian became the primary educational institute in the Southern Dynasties. The Sixteen Kingdoms and Northern Dynasties also created their own schools but they were only available for sons and relatives of high officials. The Northern Wei dynasty founded the Primary School of Four Gates.