I think this is because all of the professions cited are somewhat standardized, with most teachers in the US being particularly standardized. Law is standardiz

I think this is because all of the professions cited are somewhat standardized, with most teachers in the US being particularly standardized. Law is standardized, by nature. Medicine is standardized, by medical boards. Police are standardized to enforce the laws. Education is standardized by the government. This kind of makes sense, if the goal of pre-secondary public education is to provide a base level of proficiency in skills and common knowledge.