Life is, in the most serious philosophical sense, about having a good time. Well, that's business for you. Lowdown behavior certainly occurs in business. It also appears in any profession. Some scientists fake the data.
Some artists turn to forgery.
And some politicians demand bribes. Yet the value of science, art, and government are not sullied by these corrupt deeds. Rather, to the extent that people engage in such corrupt deeds, they are neither scientists, artists, nor politicians. And suppose that some of the teachers graded arbitrarily, were more interested in indoctrination than teaching, or became teachers only because they liked to have sex with children. Such immoral behaviors do not invalidate education.