If you are going to give the schools a letter grade, the quality of family support for education should also receive a grade. Parents should be rated for how well they prepare their children to learn each day.
Is their child's diet and sleep adequate? Does someone see that homework is done? Do they help their child prepare for tests? Is English spoken in the home? Do they attend parent-teacher conferences? Is the child experiencing abuse in the home? Is the child living in a home under duress from unemployment, divorce, drug addiction, alcoholism or mental illness? Is there chronic absenteeism?
That many of the children experiencing these stressors have any success in school is to the credit of excellent teachers. To give the teachers a failing grade when any of these children don't make grade level is unfair and wrong.