Grades Aren't Reliable CLOZE

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Grades aren’t valid, reliable, or objective. A “B” in English says nothing about what a student can do, what she understands, where she needs help. Moreover, the basis for that grade is as subjective as the result is uninformative. A teacher can meticulously record scores for one test or assignment after another, eventually calculating averages down to a hundredth of a percentage point, but that doesn’t change the arbitrariness of each of these individual marks. Even the score on a math test is largely a reflection of how the test was written: what skills the teacher decided to assess, what kinds of questions happened to be left out, and how many points each section was “worth.” Moreover, research has long been available to confirm what all of us know: any given assignment may well be given two different grades by two equally qualified teachers. It may even be given two different grades by a single teacher who reads it at two different times (for example, see some of the early research reviewed in Kirschenbaum et al., 1971). In short, what grades offer is spurious precision – a subjective rating masquerading as an objective evaluation.

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According to this reading, how exactly are grades, not "valid, reliable, or objective"? USE YOUR OWN WORDS