Although I've looked and couldn't find anything, I'll apologize in advance if this quiz/assignment restriction has been requested, is up for voting or in development and I just don't know about it.
I would really like to see a restriction feature added to assignments/quizzes granting students access according to score(s) on one or more other assignments/quizzes. I find this type of restriction extremely useful both as a motivational tool and to help guarantee mastery.
Motivational Tool- I can create a bonus assignment/quiz accessible to students only after they have received a specific score on a previous assignment/quiz. The restriction essentially "unlocks" a specific assignment/quiz for students who have performed at a specific level I predetermined. My students work very hard to achieve a specific score on an assignment that grants them access to another assignment/quiz for bonus points.
Guaranteeing Mastery- This type of restriction is wonderful when it comes to guaranteeing mastery. For example, a student MUST receive a certain score on a quiz before (s)he is allowed to take the next assessment. Or, perhaps students are required to receive a certain score on a chapter assessment before (s)he is allowed to move on to any assignments/quizzes for the next chapter.
If this type of restriction currently exists or if there is a workaround that someone knows about, please let me know!