Take, for example, my first-grade son’s Common Core math lesson in basic subtraction. Six- and seven-year-olds do not yet possess the ability to think abstractly; their mathematics instruction, therefore, must employ concrete methodologies, explanations, and examples. But rather than, say, count on a number line or use objects, Common Core’s standards mandate teaching first-graders to “decompose” two-digit numbers in an effort to emphasize the concept of place value. Thus 13 – 4 is warped into 13 – 3 = 10 – 1 = 9. Decomposition is a useful skill for older children, but my first-grade son has no clue what it is about or how to do it. He can, however, memorize the answer to 13 – 4 – but Common Core does not advocate that tried-and-true technique.