The Magic Wand Test
Today’s New York Times “Room for Debate” discussion focuses on the value-added teacher effectiveness controversy. My entry is here. Linda Darling-Hammond, by contrast, is skeptical. She says the measures aren’t good enough and offers the following as evidence:
Researchers have found that the very same teacher looks more “effective” when she is teaching more advantaged students — and less effective when she teaches more students who are low-income, new English learners, or who have special education needs.
Darling-Hammond is confused here and it’s important to understand why.
Imagine you’re on vacation in an exotic foreign land, and you stumble upon a hidden cave, and in that cave is a gold chest, and in that gold chest is a magic wand. If you point the magic wand at a teacher, it will reveal