The A-F school grades being released today provide a textbook example of the politically driven misuse of standardized testing.

Typically, A-F grades summarize how well a student has mastered the full range of material presented in a particular class. They combine performance in a variety of areas that may include tests, papers, presentations, class participation and other factors. They also reflect level of effort: students who work hard generally earn higher grades than those who do not.

As a result, the A-F scale has acquired significant cultural weight as a moral as well as an academic judgment.

Applying this culturally weighted scale to a school’s standardized test scores is far from “transparent.” Rather, it is inappropriate, misleading and harmful.

It is inappropriate because standardized test scores reflect not a broad-based year’s worth of work, but rather a single day’s performance on a single, relatively narrow measure.

It is misleading because even on this narrow measure, A-F grades do not accurately convey what an individual school has accomplished during a year. Teachers at schools where many students struggle can work far harder and accomplish far more than teachers at schools with more privileged students, yet have their schools given far lower grades.

It is harmful, because it forces schools to prominently display an inappropriate and misleading evaluation of their teachers and students, thus misinforming the public. In addition, the high stakes it attaches to test scores force schools to spend additional time and effort preparing for these narrowly-focused tests at the expense of material of equal or greater value, as well as student and teacher morale.

It is no surprise that the major backers of A-F grading also champion the dismantling of traditional public schools through measures such as private school vouchers.

Increasing the role played by test-score growth in the grades’ calculation would make them a somewhat more accurate reflection of a school’s test-related accomplishments. It would not, however, address the basic problem that comes with prominently grading schools based on a single day’s performance on a single, relatively narrow measure. Rather than simply tinkering with this problematic approach to school evaluation, legislators should scrap it.

For a concrete example of the problems of A-F grading at an individual school, see: http://www.newsobserver.com/2013/10/11/3273018/how-allowing-nc-schools-to-be.html