For years, President Obama has been a vocal booster of early childhood education. In his past two State of the Union addresses, he has called on Congress to help fund preschool for every child in the country.

"Research shows that one of the best investments we can make in a child's life is high-quality early education," Obama told Congress in January.

The president even put a price tag on his plan: $75 billion over 10 years, he said, would help every state provide preschool to every 4-year-old — to be paid for by raising cigarette taxes by 94 cents a pack.

But just what is quality preschool? It's difficult to debate the merits of early childhood education, and to argue that every child — indeed, the nation as a whole — will benefit from better access to preschool, without first defining what exactly constitutes a "high quality" model.

http://www.npr.org/2014/04/22/304563233/what-exactly-is-high-quality-preschool