When a course originally did not have tiers, students who enrolled at that time are granted full course access to ALL new lessons-- even when tiers are added.

When tiers and new lessons are added later, the system does not restrict access for previously enrolled students, so they get access to things they shouldn't have (eg, at higher tiers).

I would like to be able to assign previously enrolled students to a tier (when tiers are added), or to restrict students' access to new lessons if they enrolled before tiers were added.