Training time varies from school to school. External teachers refer to teachers with teaching qualifications recognized outside the school, or professors or experts with high reputation at home and abroad to teach in the school. On the one hand, external teachers can make up for the shortage of school teachers; On the other hand, it can further strengthen the academic research of schools. In the process of hiring teachers, different schools have different training time. Teachers hired outside the establishment are temporary teachers, also known as post teachers, belonging to a school. Without establishment, you can't be promoted or transferred. Non-staff teachers sign fixed-term employment contracts, and their wages are mainly paid by the school. There is no normal salary, medical care and health protection after retirement.