My new book, From Preschool to Prosperity (available free as a pdf, for $0.99 on various e-book platforms, and also in hard copy form), explains why the research evidence for the effectiveness of early childhood education is credible.

Among this credible evidence is the oft-cited evidence from several well-done random assignment experiments. Despite arguments from some critics, such evidence remains relevant to today’s early childhood programs.

The most relevant random assignment experiments to today’s early childhood programs are Perry Preschool, the Abecedarian Program, and several experiments with the Nurse Family Partnership Program. Perry Preschool, run in Ypsilanti Michigan in the early 1960s, found evidence that half-day preschool at ages 3 and 4 increases adult earnings of former participants by 19%. The Abecedarian program was full-time child care and pre-K from birth to age 5, conducted in North Carolina in the 1970s. This program’s effects on adult outcomes predict an improvement in adult earnings of former participants of 26%.  Abecedarian also causes increases in earnings of parents of the child participants. The Nurse Family Partnership program, which provides one-on-one home visits by nurses to disadvantaged first-time mothers from the pre-natal period to age 2,  has been experimented with in various locations over the past 30 years. NFP’s  effects on outcomes for former participants predict an increase in adult earnings of 3%, and the program also produces significant earnings effects for the mothers.

Critics have argued that this research evidence is of limited relevance to today’s early childhood programs. The argument is that these experiments look at small-scale programs designed and run by researchers, and that it would be difficult or at least too expensive to duplicate these programs’ success today at a large-scale.

However, the Abecedarian program and the NFP program are both being run today, in some form. The current Educare program is designed similarly to the Abecedarian program. The NFP program is being sponsored around the U.S.  These programs are expensive, but they can apparently be run at a large scale in many locations. Because these programs have a high benefit-cost ratios, these programs’ high costs are outweighed by even higher benefits.

Furthermore, even Perry Preschool is more similar to today’s preschool programs than is sometimes realized. Perry used certified teachers paid public school wages. So do many successful preschool programs today, for example the programs in Tulsa and Boston. Perry was a half-day program at ages 3 and 4. Some programs today, such as the programs in Tulsa and Boston, are full-day programs at age 4, which has both advantages and disadvantages compared to Perry’s design. Among the advantages is that a full-day program finds it easier to elicit participation from a wide variety of families, because it does more to solve the child care problem for working parents. Perry had a well-designed curriculum, as do many of today’s preschool programs, for example the Boston Pre-K program has had success with the Building Blocks curriculum.

One advantage Perry Preschool had over current preschool programs was smaller class-sizes. Perry had class sizes that averaged 13 students to 2 teachers, whereas most preschool programs today would have larger class sizes, on the order of  15 to 20 students to 2 teachers.  Class size should make some difference to both benefits and costs of any educational program. Based on evidence from studies of class size in early elementary school, while lower class-size may pass a benefit-cost test, it seems unlikely that there is some dramatic differences in the relative cost-effectiveness of pre-K at a class size of 13 students versus a class-size of 15-20 students.

Early childhood education has more evidence for its effectiveness from random assignment experiments than does virtually any other social or educational program. We have more evidence for the effectiveness of early childhood programs than we do for the effectiveness of, for example, 3^rd grade. With 3^rd grade we can’t run a random assignment experiment that varies program access, because this intervention already has universal access. But we’ve run such experiments for early childhood programs, and found evidence of success for programs that are similar enough to today’s programs to be relevant to the current policy debate.