Increasing both knowledge and acceptance of evolution are important outcomes of efforts to educate our students about the theory of evolution. Data were collected in the context of an 11-day short course focused on examining the evidence for evolution at a suburban STEM school in the Midwestern United States to answer the following research questions: (1) What effect did this course have on knowledge and acceptance of evolution? (2) How did cognitive and affective factors support growth in understanding of evolution in this evidence-centered educational intervention? This short course, comprising 21 students, focused on exploration-based activities allowing students themselves to collect evidence for evolution. We found significant gains in knowledge of microevolution and macroevolution, and found that both prior knowledge and acceptance of evolution were important in facilitating students' conceptual growth.