Now that it's all liberalized, why should the school check the health code?

It is prone to cluster epidemics. The reason why schools still need to check the health code is because it is prone to cluster epidemics. The "health code" is based on real data, which can be generated by citizens or people who have returned to work through their own online declaration and background check. As an individual entering and leaving electronic certificate locally, the QR code can be declared once, which is universal in the whole city.