The teacher knows best what homework should be assigned. Some nights it might be only a small assignment. Over a weekend, assignments might be extensive. An advanced student might get a different project than a student struggling with a given subject. Second, time limits have little value.
Teachers are under heavy pressure to be accountable for how well students perform.
Teachers should be accountable, but not with unneeded encroachment on their responsibilities. Professionals know what and how to teach. If they do not perform well, they should be dismissed. But the last thing any competent teacher needs is senseless meddling from the school board. The board meant well but was misguided.