A quasi-experimental method and test-retest design were used to explore the impact of participating in test preparation, whether the impact of test preparation depends on the first ACT® score, and the impact of specific test preparation activities. Test preparation improved students' retest scores and this effect did not differ depending on students' first ACT score. Working with a private tutor improved retest scores for those who reported preparing, whereas engaging in other test preparation activities was not statistically related to score gains. Students who reported feeling inadequately prepared for the second test had ACT Composite scores that were lower than those students who felt adequately prepared.