In the 1970s and 1980s, the French conducted an experiment with 2,000 students to determine whether sending children to preschool at age two was worth the public expense. The results were remarkable. After seven years of elementary school, disadvantaged students who had started preschool at age two had fully caught up with their more advantaged peers, while those who had started at three didn’t do quite as well, and those who had started at four trailed still further behind. A good preschool, it turned out, had highly egalitarian effects. A very early start, followed by systematic elementary schooling, can erase much of the achievement gap, though the payoff isn’t fully apparent until the later grades—a delayed effect that is to be expected, given the slowness and cumulativeness of word-learning.
To grasp the significance of this remarkable result, it’s important to grasp the extreme difficulty of narrowing the verbal gap between advantaged and disadvantaged students. The problem has been called the Matthew Effect, an allusion to Matthew 25:29: “For unto every one that hath shall be given, and he shall have abundance: but from him that hath not shall be taken away even that which he hath.” Advantaged students who arrive in the classroom with background knowledge and vocabulary will understand what a textbook or teacher is saying and will therefore learn more; disadvantaged students who lack such prior knowledge will fail to understand and thus fall even further behind, relative to their fellow students. This explains why schooling often fails to narrow the gap and may even widen it.
–E.D. Hirsch, excerpted from A Wealth of Words