Over this month, I’ll provide brief responses to some questions I have received at various talks I have given about early childhood programs.

Today’s question is “Why should I believe that early childhood programs work? After all, every program claims it works.”

You should believe that early childhood programs work because we have better evidence than for other programs. For early childhood programs, we have random assignment experiments in which we have (metaphorically) flipped a coin, and said heads you go to preschool, tails you don’t.

We know more about whether preschool works than about whether third grade works, or whether tax cuts work – because we haven’t been willing to flip a coin to randomly assign some children to not attend third grade, or some businesses not to receive a tax cut. With random assignment, we know that the kids who went to preschool, and those who didn’t, are comparable in all their characteristics, both those we can observe, and those we can’t observe.

We’ve followed up on these programs by asking the participants in these experiments annoying questions about their lives many years later: whether they were assigned to special education in K-12, whether they graduated high school, whether they had problems with the legal system, and what kind of career and earnings they have as an adult. The verdict from these rigorous scientific experiments, similar to experiments in medicine, is clear: high quality early childhood programs work, in that they significantly improve educational attainment and adult earnings.