Preparing for exams in introductory biology classrooms is a complex metacognitive task. Focusing on lower achieving students (those with entering ACT scores below the median at our institution), we compared the effect of two different assignments distributed ahead of exams by dividing classes in half to receive either terms to define or open-ended metacognitive questions. Completing metacognitive assignments resulted in moderately higher exam scores for students on the second and third exams. Metacognitive assignments also improved accuracy (difference between predicted and actual exam scores) for the second and third exam in lower ACT students, but that improvement was driven largely by higher exam scores in the metacognitive group. Thus, despite the fact that the metacognitive assignments specifically asked students to reflect on their previous exam performance, their previous estimates and predict how well they expected to perform on the exam they were preparing for, there was little evidence that these assignments influenced lower achieving students' confidence levels any more than assignments where students defined terms. While understanding relevant terms was certainly important in this course, these results highlight that open-ended metacognitive prompts may improve exam scores in some students in introductory biology classrooms.