Feedback indicating how well students are performing during a learning task can be very stimulating. In this study with a pre- and post-test design, the effects of two types of performance feedback on learning results were compared: feedback during a learning task was either stated in terms of how well the students were performing relative to other students (social comparison feedback) or relative to an absolute criterion (criterion-based feedback). Thirty-four students in secondary vocational engineering education were randomly assigned to one of two conditions. In both conditions, students worked together in small groups. All groups completed a math learning task, during which they received either social comparison feedback or criterion-based performance feedback. The findings showed that the type of feedback had a strong effect on learning outcomes: the post-test scores and gains of students in the social comparison condition were significantly higher than those of students in the criterion-based feedback condition.