For every taxpayer dollar spent on government-run universal preschool, society will reap greater dollars in future benefits.

This claim is based on a RAND study that uses data from previous research done on a Chicago preschool program targeted at low-income children. However, extrapolating the benefits of the Chicago program to a statewide California universal preschool program that does not yet exist is empirically questionable.
Further, other studies note that any benefits of preschool fade away by the middle of elementary school. A 2006 study by UC Santa Barbara researchers found that “the achievement impact of preschool appears to diminish during the first four years of school.” This fade-out effect is due to the poor performance of public K-12 schools.

Middle- and upper-income children benefit from government-run universal preschool.

According to RAND, the one study that examined the long-term benefits of preschool on non-disadvantaged children “found that children participating in preschools not targeted to disadvantaged children were no better off in terms of high school or college completion, earnings, or criminal justice system involvement than those not going to any preschool.” Thus, preschool had no long-term beneficial effect on middle-income and upper-income children.
Studies of short-term benefits to middle- and upper-income children are limited and inconsistent. A recent study of Oklahoma’s universal preschool program found some achievement improvement for non-disadvantaged children, but a previous study of the Oklahoma program by the same researchers found no achievement gains for middle- and upper-income children.

Universal preschool in California will be similar to successful model preschool programs.

In response to the decidedly mixed results of preschool, the proponents of Proposition 82 contend that the preschool program promoted in the initiative will mirror the more successful preschool experiments such as the program for low-income children in Chicago. However, key features of the Chicago program, such as a multi-faceted parent involvement program, home visitations, health screenings, speech therapy, and nursing services, are not included in preschool program outlined in Prop. 82.

Higher teacher education requirements for preschool teachers will improve student achievement.

Under Prop. 82, preschool teachers will have to have a bachelor’s degree and a teaching credential. However, in a recent study, UC Berkeley researchers conclude: “Claims that a Bachelor’s degree further advances child development simply cannot be substantiated by studies conducted to date.”
Thus, a recent analysis of Georgia’s universal preschool program found that whether a teacher had a BA in child development, a BA in some other field, or lesser training, made no difference in student performance across nine different measures of thinking and reasoning skills and social development. A study by the National Institute of Child Health and Human Development found that the effect of caregivers, including teachers, on children’s development was less than a quarter of the effect of mothers’ parenting practices.

There is no downside to exposing children to preschool.

According to a 2005 Stanford-UC Berkeley study, “attendance in preschool centers, even for short periods of time each week, hinders the rate at which young children develop social skills and display the motivation to engage classroom tasks, as reported by kindergarten teachers.” The study notes especially, “This slowing of typical rates of social-emotional growth is particularly strong for Black children and for children from the poorest families.”

“Prop. 82 supporters claim the cost is worth it, citing research that purports to show that for every dollar invested in government-run universal preschool, society receives $2.62 in long-term benefits such as higher student performance and lower levels of criminal activity,” said Mr. Izumi. “Yet, this claim and many others made by the proponents of Prop. 82 are built on a house of cards of limited, inconsistent and non-existent real evidence. In other words, the case for Prop. 82 is built on a series of myths.”