Oklahoma is one of several states that provides universal voluntary pre-K to four-year-olds, as of 1998. In the fall of 2005, we embarked on a new research project in Tulsa, OK. During the 2005-06 school year, we observed almost all of the preschool classrooms run by Tulsa Public Schools (TPS) and by CAP of Tulsa County Head Start. We followed a cohort of students who had attended these pre-K programs and compared them to students who did not. Here is what we have learned. (author abstract)