Research studies show that students' grades are more predictive than test scores of their future academic success, including high school and post-secondary outcomes. Chicago Public Schools (CPS) recognizes the importance of grades through its longstanding "Bs or Better" campaign. Yet within CPS, boys' grades are consistently lower than girls' grades. CPS leaders and educators want to meet their goal of Bs or better and strong educational outcomes for all students, and they are in conversation about how they're supporting boys. This study aims to provide insights into this difference in boys' and girls' grades in Chicago by looking first at one grade level and one subject area--ninth-grade math (algebra and geometry)--using two school years of data, 2016-17 and 2017-18. The findings are specific to math students in these years, and also suggest what may (and may not) be driving differences in other grades and subjects. [Additional funding for this report was provided by the Hyman Milgrom Opportunity Fund at the University of Chicago and the Consortium Investors Council.]