Examples:
- A lot of redundant homework is assigned, quantity over quality. Some students with external duties (e.g. family, work) are just unable to deliver all the homework, and thus get lower grades, even though less homework would be enough to demonstrate ability in a topic;
- Deadlines are set too close to an homework availability date, so students with external duties are sometimes unable to meet them;
- Students in affluent families could be helped by third parties with their homework; it's hard to verify that;
- Students that do a bad homework or fail an exam should be able to retake it, since it's easier to have a "bad day" if your family has issues.
The point is measuring actual student ability, not busywork throughput or the willingness to meet arbitrary deadlines.