Students' attitudes can be influential in the emotions experienced in mathematics learning and achievement at school. Two important judgements, according to Control-Value Theory are degree of control a student has over, and the value attached to, learning activities or outcomes. Appraisals of control and value are believed to play a central role in the emotions experienced when learning, and subsequent achievement. Achievement, in turn, can strengthen or weaken control-value appraisals. In the present study we set out to examine the bidirectional relations between control-value appraisals and a key emotion experienced in the mathematics classroom, namely anxiety. In addition, we tested the proposition that control-value appraisals are indirectly linked to achievement, mediated by classroom-related anxiety. The participants were 1242 Year 5 students (49% female), with a mean of 9.3 years, from 24 English primary schools. Self-report data for anxiety, and control-value appraisals, were collected over two waves (separated by seven months) and mathematics achievement collected from a classroom test one week later. Results from a structural equation model showed bidirectional relations between higher anxiety and lower control. Although anxiety predicted lower value, value was unrelated to subsequent anxiety. Higher control at the first wave of measurement was related to higher mathematics achievement, mediated by lower anxiety, at the second wave. These results underscore the importance of reducing anxiety when learning mathematics and suggest that intervention could achieve this outcome by reducing anxiety directly or by strengthening control.