Before World War II, countries all over the world generally implemented the dual-track education system, that is, the education system of preparing for further studies and preparing for employment. These two tracks are almost impassable. The main drawback of the dual-track system is that students lack the opportunity to re-choose, and students who cannot be promoted to a higher level lack the ability to adapt to social life. After World War II, the proportion of comprehensive middle schools has gradually increased, and there has been a trend of professionalization of general education and popularization of vocational middle schools.