Quiz

Hi John,
Currently I'm retired from teaching, but the way I used to handle this was by having a totally separate Random Quiz course. I enrolled all my students in it. Each "subject" had a ten question quiz that could be taken as many times as a student want to. The questions were selected randomly from the appropriate "subject" question bank, in which I usually had forty or more questions. Students concentrated on the quiz/quizzes appropriate for the current week. Having this setup of a separate course made it so I never had to worry about accidentally messing up their grades in the course that actually counted.
If you use your method of including the practice quizzes in the actual course, you can go into grade setup and hide the practice items. You will need to remember to do this every time you add a new practice quiz. Being forgetful myself, that's why I opted for a totally separate Random Quiz course.

I do something like this in my courses except that I like to give students credit whenever they do anything. I call these "self-assessments." It would be up to you to decide how many quiz points to provide. You could also group all of your quizzes into one grade book category, and then make the category be worth what ever you want (including 0) toward the students grade. I have found that if something is graded, that students then have an incentive to do these self-assessments. I also retain their highest score, and this is what then goes into their grade book. So students can never "do worse" by re-attempting a quiz.

Al offers some good ideas, too. In my case, I prefer to built these self-assessments into my courses. But sure, they could be put into another course.