It's easy to dismiss test scores as reflecting a school's socioeconomic makeup more than teaching abilities, admits L. A. Times Op-Ed editor Sue Horton. And she agrees that much of learning, and excellent teaching, "involves intangible things that happen during the school day, interactions between students and teachers that defy quantification." However she says the public should know if the data shows that some public school teachers are far better than others at helping kids master the essentials. 'Value-added' analyses could identify the most effective teachers and what they are doing right.