What should I say if my child says, "Am I stupid?"

Say clearly, "you are not stupid." Explain—citing their areas of strength—that intelligence and ability can't be measured on a single yardstick, that everyone has strong and weak abilities, and that people remember and think in different ways. Convey that "a test score isn't a person's worth," and that weaknesses can be supported with tools and adjustments. What matters most is that the child doesn't come to believe they're "a no-good child." Day-to-day, recognizing them in many dimensions—effort, ingenuity, kindness—not just results, is what supports them.