The Magic of (Pre)School

When I think of the most important lessons I learned from birth to grade 12, I think of all the wonderful things I learned before I entered compulsatory school. When I think of the type of person I am today, I remember all those diverse experiences, social interactions, and moments of play that formed my pre-education. I seem to draw a blank at middle-school and the only memories I have of high school are the after-school activities I engaged in. All anecdotes aside, what are the large-scale long-term effects of preschool?