Metacognitive regulation occurs when learners regulate their thinking in order to learn. We asked how introductory and senior-level biology students compare in their use of the metacognitive regulation skill of evaluation, which is the ability to appraise the effectiveness of an individual learning strategy or an overall study plan. We coded student answers to an exam self-evaluation assignment for evidence of evaluating (n = 315). We found that introductory and senior students demonstrated similar ability to evaluate their individual strategies, but senior students were better at evaluating their overall plans. We examined students' reasoning and found that senior students use knowledge of how people learn to evaluate effective strategies, whereas introductory students consider how well a strategy aligns with the exam to determine its effectiveness. Senior students consider modifying their use of a strategy to improve its effectiveness, whereas introductory students abandon strategies they evaluate as ineffective. Both groups use performance to evaluate their plans, and some students use their feelings as a proxy for metacognition. These data reveal differences between introductory and senior students, which suggest ways metacognition might develop over time. We contextualize these results using research from cognitive science, and we consider how learning contexts can affect students' metacognition.