MGLS data offers information on the characteristics and cognitive outcomes of students who were enrolled in the 6th grade in public schools in the 2017-2018 school year and two years later in spring of 2020 when most students were in the 8th grade. The MGLS data are organized into student and school folders, each containing .txt data, data input files for SAS, SPSS, Stata and R survey software packages. A .csv version of the data is also provided.