The negative thoughts that anxious children experience while sitting for an exam consume working memory resources at the cost of resources for performing on the exam. In a randomized field experiment (N = 117) with primary school students, we investigated the hypothesis that stimulating students to look through the problems of a math test before they start solving them would reduce anxiety, release these anxiety‐related working memory resources, and lead to higher test performance than not allowing students to look ahead in the test. The results confirmed the hypothesis, indicating that the positive effects of looking ahead applied to all students, regardless of their anxiety level (low, medium, or high). The results suggest that by looking ahead in a test, less working memory resources are consumed by intrusive thoughts, and consequently, more resources can be used for performing on the test. Theoretical and practical implications of the results are discussed. Copyright © 2014 John Wiley & Sons, Ltd.