maybe smth else?
Actually passwording works quite well for us. Teachers can easily change passwords as necessary. The password is only need to enroll in the course. Once enrolled, the student no longer needs the password.
Here's an idea:
The required course would not have a password necessary for enrolling.
Another option would be to have an end of course "assignment" that emails the facilitator or instructor for the required course and that person can check progress through the required course and then send back the password or even enroll the student in the next course by using "assign roles" in that course.