At the retreat Ed spoke about the long term Chicago study that SCIENCE published in June 2011.  This study is probably the first that legitimizes with hard data the fact that Pre-School has a long term positive impact on the lives of students as they continue in school and life.   Here are two links to the data:

1.  Reprints from two articles reporting the results of the the long-term study that  followed 1,539 children born in 1979-80.

2. Actual study as reported in SCIENCE.