Research on the attrition of teachers of color suggests that, under certain organizational conditions, they leave teaching at higher rates than other teachers. Additionally, research has identified microaggressions experienced by Black teachers. Building on the literature, we explored how racism and microaggressions may help us understand Black mathematics teachers' attrition. We designed and administered the Black Teachers of Mathematics Perceptions Survey and found that teachers' experiences of microaggressions accounted for most of the variance in our modeling of teachers' thoughts of leaving the profession. These data reveal that anti-Black, racist microaggressions should be addressed as organizational conditions to be mitigated. From a critical quantitative perspective, the data reveal sociocultural and sociopolitical influences that often go unnoticed in large-scale policy work.