High school students report high computer anxiety. The addition of three computer anxiety dimensions (i.e., Affective Anxiety, Damaging Anxiety, and Learning Anxiety) improved the prediction of computer course grades beyond that afforded by the differences in academic achievement. 700 Turkish high school students (386 boys, 314 girls) enrolled in high school computer courses participated. The Computer Anxiety Scale and a personal data sheet were used to collect the data in the study. Computer course grades were positively related to students’ academic achievement but negatively related to the three anxiety subscales. When differences in academic achievement were controlled in multiple-regression analyses, anxiety dimensions were not significantly related to course grades. Anxiety has a more detrimental effect on students with lower academic ability than on those with higher academic ability.