Expectancy-value theory (EVT) is a popular framework to understand and improve students' motivation. Unfortunately, limited research has verified whether EVT predictions generalize to students with low levels of cognitive ability. This study relies on Grade 5 and 8 data from 177 students with low levels of cognitive ability and a matched sample of 177 students with average to high cognitive ability from the German "Project for the Analysis of Learning and Achievement in Mathematics." Results showed that students with low levels of cognitive ability were able to differentiate EVT components. Both groups demonstrated a similar downward developmental trend in motivation from early to middle adolescence, and similar relations between EVT components and levels of efforts, self-regulation, and mathematics class grades.