Academic underachievement has been associated with serious long term consequences for children and adolescents, including poorer outcomes within occupational, social, and health domains. Research has shown that student's cognitive abilities, such as working memory and verbal reasoning, significantly predict achievement outcomes. However, identifying symptomatic factors that influence achievement may be more beneficial in informing appropriate intervention and prevention efforts. In order to determine the impact of such factors on achievement, the current study investigated the degree to which anxious and ADHD symptoms were associated with reading, writing, and mathematics achievement in a clinical service-seeking population beyond the variance explained by working memory and verbal reasoning. Correlations indicated significant positive relationships between cognitive variables, anxiety variables, and achievement outcomes, and a negative relationship between inattention and achievement outcomes. Furthermore, regression analyses indicated that symptomatic factors explained a significant amount of variance in reading and writing, but not mathematics achievement. Inattention was the only individual symptomatic variable that significantly predicted reading and writing achievement within the final regression models.