When should instructors fire students (ask students to no longer participate)?
This is a more challenging issue in the corporate and government world, where training is more thought as a service, or a requirement, than the academic.
This gets more interesting when simulations are introduced, and there is real work required from a student, not just showing up. Courses can also be several sessions, not just one.
Some people view percentage who finish the course as a critical metric. And any pure e-learning course never automatically jettisons a student.
But if students weakly approach a course, they go through the motions but don't push, then that messes up any ROI and evaluations. The passive students also can become the biggest critics, resolving their own dissonance by lowering the view of the course instead of raising their own expectation for growth.