This article explores which students engage in formal preparation for college entrance exams (e.g., SAT tutoring). Despite significant national attention to test prep, we know little about who participates—apart from emerging research supporting popular opinion about income inequalities in access to prep classes and tutors. Using data from the National Household Education Survey (2007), I evaluate the impact of general demographic, student-level, and school variables on the likelihood of prep. A key finding of these analyses is that pooling high school students can obscure differences in participation in test prep by grade. The likelihood of prepping increases for each grade, with 42% of 12th graders but only 8% of 9th graders participating. Black non-Hispanic students are more likely to participate in test prep, and there are also significant interaction effects of race and grade level on prep, with black 11th graders having the highest predicted probability of prep. Student and parent involvement are statistically significant across most models, but with relatively small substantive association. I argue that test prep is a time-sensitive variable, and raise theoretical questions about similar variables in cross-sectional data that represent time-sensitive events or processes.