The Baltimore Early Education Data Collaborative began after the release of BERC’s report Early Elementary Performance and Attendance in Baltimore City Schools’ Pre-Kindergarten and Kindergarten in March 2012. That report introduced numerous partners who worked in early education in Baltimore and the through conversations about how much we could learn if we shared our data, led to the creation of the Early Education Data Collaborative. This brief provides the technical background on the data and methods used in our work. (author abstract)