The school year is ending in the United States and I hear a lot of chatter about grades. The most common complaint I hear is that one kid or another scored high on tests but ended the year with a disappointing grade for not turning in all of the homework. Does that grading system make sense when the point of the homework is to prepare kids for tests?
In the real world, results are what matter the most, as long as you arrive at the results legally and ethically. If an adult makes a sales presentation and nails it, no one cares how many hours she practiced before the meeting.
My suggestion is that schools issue homework grades that are separate from test grades. That way you can get a better sense of what is going on with each kid. Blowing off homework is a valid strategy if you're confident you will ace the test. It's especially valid if skipping homework creates time for a kid to participate in additional extracurricular activities.
Would you rather hire someone who cared little about homework but aced all tests, or someone who was dependable and hard-working but underperformed at test time? The right answer is that it probably depends on the job description. If you're hiring a security guard, you might want the reliable candidate. If you're hiring a research scientist, go for the test scores. If you're hiring a lawyer, you probably want both qualities.
Not all homework is created equal. If an assignment involves writing a paper, for example, obviously that grade needs to be included with test scores. I would only strip out the memorization and practice types of homework assignments and grade them separately.
At one point in our history it might have made sense to blend the scores for homework performance and tests. A combined score probably did a good job of predicting how well a kid might someday run the family farm. But in the information economy, brilliance and reliability go separate directions. We want brilliant people designing microchips and reliable people manufacturing and selling them.