How did the school discover that the parents' health codes changed color at school?

Under normal circumstances, the school can't see it unless it is required to upload information. The community and the police station should know about this and contact you. However, if the color of the health code changes, it is recommended to contact the school actively. After all, the epidemic is still serious and there are many students in the school. If there is any situation, you should contact the school or community as soon as possible.