This study of Maryland State Department of Education data on K-12 public school students in Maryland for 2009/10, 2010/11, and 2011/12 examines whether exclusionary discipline (suspension and expulsion) is given out in a way that has a disproportionate impact on Black and other racial/ethnic minority students relative to White students, and on students in special education relative to other students. These disparities are a concern because exclusionary discipline has been linked to poor academic achievement, grade retention, recurrent misbehavior, dropout, juvenile delinquency, and other undesirable out-comes (Anfinson et al., 2010; Fabelo et al., 2011; Forsyth et al., 2013; Gregory, Skiba, & Noguera, 2010; Kinsler, 2011). This study uses Maryland State Department of Education data on K-12 public school students for 2009/10, 2010/11, and 2011/12 to answer two questions on disproportionality in student discipline in the 24 Maryland school systems: (1) Is exclusionary discipline (suspension and expulsion) given out in a way that has a disproportionate impact on Black and other racial/ethnic minority students relative to White students? (2) Is exclusionary discipline given out in a way that has a disproportionate impact on students in special education relative to other students? The study found that during these three school years: (1) The percentage of Maryland students receiving out-of-school suspension or expulsion dropped from 5.6 percent in 2009/10 to 5.0 percent in 2011/12; (2) Because rates of out-of-school suspension and expulsion decreased more rapidly for White students than for Black students, disproportionality between Black and White rates increased in 2011/12, the most recent year examined; (3) For the same type of infraction, Black students had higher rates of out-of-school suspension or expulsion than did Hispanic and White students; (4) In all 24 Maryland school systems Black students received out-of-school suspension or expulsion at more than twice the rate of White students; and (5) Statewide, students in special education were removed from school at more than twice the rate of other students, even though the number of out-of-school suspensions and expulsions decreased for both groups over the three years. Study implications indicate exclusionary discipline exacerbates behavior and attendance problems and contributes to poor academic performance, all of which make dropping out of school more likely (Bridgeland, DiIulio, & Morison, 2006; Gleason & Dynarski, 2002). Students who are suspended or expelled miss classroom instruction time and thus fall behind in their coursework, becoming twice as likely as other students to repeat a grade (Fabelo et al., 2011). Suspension has also been linked to a greater likelihood of recurring misbehavior and future suspension (Anfinson et al., 2010). Although the study findings indicate some large disproportionalities in discipline-especially for Black students and students in special education-the data cannot establish the source of these disparities. Collecting discipline data describing the severity of each type of infraction would help administrators and educators move toward more equitable disciplinary practices. A next step for the Maryland State Department of Education is to identify the most appropriate "tipping point" in disproportionality that will require school districts to develop remediation plans to ensure fair disciplinary practices for all students. "Calculating Relative Rate Ratios" is appended. [This report was prepared for the Institute of Education Sciences (IES) by Regional Educational Laboratory Mid-Atlantic administered by ICF International. It summarizes the findings of Porowski A., O'Conner, R., & Passa, A., 2014, "Disproportionality in school discipline: An assessment of trends in Maryland, 2009-12 (REL 2014-017), ED544770.]