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President Obama's 2016 budget includes a renewed push for the broad liberal priority of universal preschool. The budget would invest in a "preschool for all" initiative trying to expand access to high-quality Pre-K programs for 4-year-olds from poor and moderate-income families, and it includes $750 million in grant funding to help states create and expand such programs.

Universal preschool isn't a new proposal for Obama — he's has been talking about it since 2013 (related debates over universal child care in America also go back decades). Pre-K has become a rallying cry for liberals from Seattle to New York who believe that investing in young children from poor families may be the best way to narrow inequality as they grow up (it's also a good way to make it easier for their parents to work in the present).

Beyond inequality, though, there are a lot of arguments for backing universal Pre-K, many of which aren't particularly lefty. Early childhood education, for starters, is one of the most efficient places we can investment public money, with broad implications for the costs of social services that have seemingly little to do with school. If you don't want to spend a lot on incarceration or welfare or Medicaid, you should spend money on preschool.

Nobel Prize-winning economist James Heckman has found that the earlier we invest in low-income children, the higher the returns for both society and the kids themselves:

These returns show up years later in everything from higher college graduation rates, to greater earnings to less criminal activity. These benefits, in turn, mean that society ultimately reaps more tax revenue from low-income children who grow up to stable jobs, and it means we can spend less on the costly consequences — like incarceration and unemployment — of not investing in poor children. Heckman and colleagues estimated that one model high-quality program run the 1960s, the Perry Preschool Project, yielded a conservatively estimated rate of return of 14 percent — better, he points out, than standard returns on stock market equity.

Another body of research from neuroscience helps to explain Heckman's graph above. Increasingly, we're realizing that these early years before children ever show up for the first day of kindergarten are crucial for their brain development, and for fostering the very kinds of cognitive and social skills — concentration, impulse control, emotional stability — that help them do well later in school and in the job market.

What happens at home in these early years, as upper-income parents read to their children while working single moms have little time to, also helps explain why poor children show up on the first day of kindergarten already far behind. Spend money on them as 4-year-olds, in short, and you boost their chances of graduating college 14 years later, or paying taxes two decades down the road, or becoming parents in their own right who will be better prepared to raise their own kids.

The big education reform movements in the U.S. over the last 175 years created universal elementary school, then universal high school. The advent of land grant colleges and the G.I. Bill further opened up affordable college to ever more people. The next reform chapter, which Obama is bracing, says that what's needed now is a new national commitment to the very first stage of education that comes before all of these others.