This paper explores gender, racial, and socioeconomic disparities in school discipline to test alternative hypotheses concerning disproportionate school discipline. Although disproportionate representation of minority students, especially African-Americans, in school disciplinary procedures has been documented almost continuously for 25 years, few researchers have examined the factors contributing to that disproportionality. In the study reported here, it was found that racial and gender discrepancies in school disciplinary outcomes were consistent regardless of the methodology employed, though socioeconomic disparities appeared to be less robust. There was no evidence that racial disparities disappear when controlling for poverty status; instead, disproportionality in suspension appeared to be due to prior disproportionality in referrals to the office. Although discriminant analysis suggests that disproportionate rates of office referral and suspension for boys are due to increased rates of misbehavior, no support was found for the hypothesis that African-American students act out more than other students. Rather, these students appear to be referred to the office for less serious and more subjective reasons. These results argue that disproportionate representation of African-Americans in office referrals, suspensions, and expulsions is evidence of a pervasive and systemic bias that may be inherent in the user of exclusionary discipline. (Contains 85 references.) (RJM)