When they also run programs, and when it’s a conspiracy, it can be close to impossible.
UCLA – a pretty respectable school – handed the running of its orthodontics school over to a set of buddies who made a point of admitting students from way-rich middle east kingdoms. Once in residence, these students were ordered to come up with, er, supplemental fees in the tens of thousands of dollars, and if they didn’t they’d be out on their oil-rich asses.
Not sure how the school figured out what was going on, but for reasons of its own the school – after throwing the members of the conspiracy out – did nothing by way of prosecution of anyone, and worked hard to keep a report about their malfeasance secret.