WSIPP conducted a retrospective evaluation of Washington State's early childhood education program, ECEAP, at the direction of the 2013 Legislature. To analyze the impact of ECEAP, we identified a group of children who received food assistance benefits when they were three- or four-years old and subsequently attended Washington State public schools. Some of these children attended ECEAP and others did not. We developed a statistical model to determine whether attending ECEAP had any impact on student academic outcomes. We found that ECEAP has a positive impact on third, fourth, and fifth grade test scores. ECEAP's impact on test scores is almost twice as large as the average effect we found when we reviewed research on early childhood programs in other states. At this time, we are unable to conduct a complete benefit-cost analysis because we cannot measure whether ECEAP affects longer-term outcomes such as high school graduation and crime. WSIPP would be able to conduct an evaluation of these long-term outcomes after 2020 when the children in the analysis are expected to graduate from high school. (author abstract)