If an employee has the freedom to quit (being easily able to find new employment and being supported by unemployment benefits) they won’t accept being treated badly by their employer.
If they don’t, then it’s a recipe for exploitation. Wage theft, sexual exploitation, unsafe working conditions, etc
This is really the same in any relationship - you can’t have an abusive marriage unless the victim is stuck in it (because of money, shame, loss of access to children, etc)
And it’s the same in education. If we expect good relationships between educators and students (and that is indeed very important) the students (as the party with less power in the relationship) must have the opportunity to quit (meaning they should be able to choose which educators in which schools they want to be taught by)