[PeterisP]

Although educating people can be done in any decent school (or no school at all) better schools do a better job of filtering people, i.e. the key tasks of ensuring that (a) that the less capable people don't get a degree from you, either because they're pushed to drop out or you filter them out during the application process, and (b) that the top cohort of capable people actually apply to your school (in many schools, their degree is an uncertain but strong indicator that you weren't good enough to get into a better school).