PRE-K….Education policy, which rarely produces unalloyed success stories, “must be a discouraging field to work in,” I said yesterday. Maybe so, but Ezra Klein reminds us that “The big bright spot, it should be said, is universal pre-k, which has not only shown itself to have massive educational benefits, but to be tremendously cost-effective as well.”

That’s true. You have to do it right, and you have to keep at it (the effects are small if you offer a year of pre-k and then nothing more), but it’s one of the few things that has proven benefits. That said, this is a good excuse to link in more detail to an article a few days ago by Chicago Tribune science writer Jeremy Manier about the different approaches to pre-k from each of the presidential candidates:

As decades of academic studies on brain development start to land in the real world, experts are divided on whether to focus new funding on infants and toddlers, or conventional preschool. Many now think some policies popular with politicians and the public, such as universal prekindergarten, may fail to reach at-risk kids at a young enough age.

….Chicago has become a national proving ground for schooling during the first three years, and is home to prominent advocates such as Nobel Prize-winning economist James Heckman of the University of Chicago, who said reaching kids before preschool could offer the best long-term economic return.

“Even at age 4 or 5 you may be starting too late,” Heckman said. “I wouldn’t say it’s hopeless to help kids after those early years, but it’s extremely expensive.”

Backers of universal preschool say the evidence for even earlier intervention is not yet solid and offering conventional prekindergarten to everyone would help build popular support for early education.

Although each Democratic hopeful is proposing dramatic increases in funding for Early Head Start, the federal program aimed at children younger than 3, they disagree on the importance of universal preschool.

Sen. Hillary Clinton’s proposals focus on extending universal prekindergarten by requiring that states offer preschool to all 4-year-olds to receive certain federal funds. Sen. Barack Obama would direct more money to the years before preschool and quadruple the size of Early Head Start, which now serves just 3 percent of eligible children. Obama describes his plan as “a preschool agenda that begins at birth.”

Officials for Sen. John McCain said the research has convinced the Republican nominee of the value of investing in early development, but he has not yet proposed changes to existing policies.

Read the whole thing for more. Bottom line: Obama and Clinton both take the issue seriously but have different priorities, different approaches, and different ideas about how best to get political support for more widespread pre-k programs. John McCain, on the other hand, basically couldn’t care less.