We evaluate the effects of grade retention on students' academic, attendance, and disciplinary outcomes in Indiana. Using a regression discontinuity design, we show that third grade retention increases achievement in English Language Arts (ELA) and math immediately and substantially, and the effects persist into middle school. We find no evidence of grade retention effects on student attendance or disciplinary incidents, again into middle school. Our findings combine to show that Indiana's third grade retention policy improves achievement for retained students without adverse impacts along (measured) non-academic dimensions. [This paper was supported by Notre Dame's Center for Research on Educational Opportunity (CREO) and the Institute of Educational Initiatives and their partnership with the Indiana Department of Education.]