Sara Mead of Bellwether Education Partners has a thought-provoking post (“How Pre-k is Like Charter Schools, and What We Can Learn from the Evidence on Each”) comparing pre-k and charter schools as educational policy interventions.  She argues that “the body of evidence for pre-k is… comparable to the body of evidence on charter schools. In both areas, we have a strong body of evidence that specific models–such as the High/Scope Perry Preschool and the KIPP network of charter schools–“work.” But we also have evidence showing that the broader range of early childhood or charter school operators are something of a mixed bag. “ Therefore, for both pre-k programs and charter schools, a crucial policy issue is “How do you design structural arrangements so as to maximize the number and reach of the highest-quality providers, and minimize the number of low-quality providers?”

Sara Mead goes on to add two caveats. The first is that pre-k is offering additional services, whereas charter schools are offering a different type of service. The second is that in many cases, existing preschool programs simply have too few resources, and that therefore simply adding more resources (e.g., lower class sizes) will help. She implicitly contrasts this lack of resources with K-12.

My interpretation of the research evidence is somewhat different.  (Although perhaps it could be argued that our interpretations are similar but place a somewhat different spin on the research results.)  My view is that for pre-k, the research evidence suggests that a pre-k program run with some attention to having reasonable quality and resources, and a reasonable focus on learning, will generally be effective. For charter schools, my view is that the research evidence suggests that on average, charter schools have been disappointing, but that some charter schools, which take better approaches to educational delivery, are quite effective.

In other words, if a “full glass” means strong research evidence of effectiveness, and an “empty glass” means no research evidence of effectiveness, I would say that the “research glass” is significantly more than half full for pre-k, while it is less than half-full for charter schools. I don’t know for sure what Sara Mead would say, but she could be interpreted as saying the “research glass” is “half-full, half-empty” for both pre-k and charter schools.

I don’t know how you “prove” how “full” the research glass is. You don’t do it by just counting studies. I am impressed by the findings that pre-k programs seem to work when run by Chicago Public Schools, and by a wide variety of states. It doesn’t seem as if you have to have pre-k programs run by some extraordinary leadership or management talent. On the other hand, it seems as if for charter schools, we frequently find that charters, on average, are no better than regular public schools. Charter schools are more effective in larger urban areas, or for lower income or lower prior achievement students. Charter schools also are more effective if they have more distinctive designs, such as the Harlem Children’s Zone or KIPP Schools.

Why might pre-k be an “easier” intervention than charter schools to make effective in a wide variety of settings? First, as Sara Mead notes, pre-k is adding additional learning time for many students. One thing we do know from educational research is that additional learning time, not surprisingly, leads to more learning. Charter schools do not necessarily add learning time. It is of interest that KIPP Schools, one of the successful charter school models, operate with a significantly longer school day and year.  The Harlem Children’s Zone schools also have more student hours in school. Maybe charter schools would be more consistently successful for more students if they always added learning time. An interesting issue is whether charter schools could consistently add learning time at the same cost per student if they were run at a large scale. Pre-k programs of course have a cost to add additional learning time, which is part of the analysis of the benefits and costs of this policy intervention.

Second, it may be that earlier educational interventions find it easier to make a difference for a wider variety of students. As various researchers have hypothesized, such as Nobel Prize-winning economist James Heckman, people may be more malleable at younger ages. In the educational research field, it certainly seems that there are more successful interventions at the elementary school level than at the high school level.  It is not impossible to change people at later ages, but the approaches to doing so might need to be more targeted at specific types of persons and more carefully designed in their goals.