Years ago I made a decision about teaching. I decided that my goal was not to teach study habits but to teach mathematics. I collected homework and graded three problems on each assignment. This makes little difference to the students who have good study habits. I could assign all odd numbered problems (which have answers) but not collect them. They could ask questions when they were stuck. When I collect written homework, I assign half odd numbered problems.
By collecting homework I am rewarding students who follow the rules, but not teaching them the consequences of not studying.
Oddly enough, the odd numbered problems were frequently wrong. They were sometimes right, but the work was incorrect. I stamped those with my stamp saying, “Your work does not support your answer.”
Sometimes I graded their clerical skills: could they copy the answers correctly. Of course, when the question was of the form,”Give an example of . . .” I would sometimes get “Answers vary” or for the student with limited clerical skills, “Answers very.”