The Big Lift™ (Big Lift) is a preschool-third-grade collective impact initiative in San Mateo County, California. The initiative is a partnership of the County of San Mateo, the San Mateo County Office of Education, and the Silicon Valley Community Foundation. Launched in 2012, the initiative aims to boost children's reading proficiency by third grade through four coordinated strategies, called "pillars": (1) High-Quality Preschool; (2) Family Engagement; (3) Summer Learning; and (4) Attendance. To date, the initiative involves seven school districts in San Mateo County that began implementing Big Lift services in the 2015-2016 or 2016-2017 school year. The RAND Corporation is conducting a multiphase evaluation of the initiative, including an implementation study of the four pillars that underlie Big Lift--"The Big Lift Implementation Study: Final Report" (ED594842)--and a series of annual descriptive analyses focused on the outcomes of children who received Big Lift services. This report is the fourth in the series of outcome studies. In this report, the authors examine the experiences and third-grade outcomes of the 2016-2017 kindergarten class, the first set of children who participated in the initiative to reach third grade. Specifically, they analyze two third-grade measures: attendance and English language reclassification status. In addition, the authors look across all the kindergarten classes for which they have data and explore the relationship between children's participation in Big Lift services prior to kindergarten and their kindergarten readiness. [For this report's technical appendix, see ED615888.]