In this paper, we evaluate the effectiveness of the first year of a federally-funded, evidence-based preschool through third grade intervention in Chicago. We use inverse probability weighting with regression adjustment to estimate the impacts of the Child-Parent Center (CPC) program on teacher assessments of school readiness for 1289 low-income preschool and 591 comparison-group participants. Results indicated significant positive impacts of the program for all domains, including literacy, math, socio-emotional development, science and total score. The percentage of CPC children who met national norms in school readiness exceeded the comparison group by 12 to 18.5 percentage points. Full-day participants experienced greater school readiness gains while program impacts were similar by family income and home language. Compared to the original CPC evaluation of children born in 1980 in which few comparison group children attended preschool, we find evidence that the contemporary implementation performs at least as well even though the current comparison group participants had alternative preschool experience. (author abstract)