According to generational theorists, the interests and experiences of incoming students have fluctuated over time, with Millennial students being more engaged and accomplished than their predecessors. This project explored data from 1974-2007 to determine the actual trends in engagement and accomplishments for three generations of students. Over three million Student Profile Section data sets were randomly selected from complete ACT College Entrance Exam records. Given the existence of significant random variability among states, all trend analyses were conducted using hierarchical linear modeling. The primary finding of this study is that current students are engaging in fewer high school activities and attaining fewer accomplishments during high school than students of the previous generation. Specifically for activities, men and students from larger class sizes were less engaged, and students with higher socioeconomic statuses, higher grade point averages, and higher ACT scores were more engaged. Overall, the results of this dissertation suggest that student affairs professionals should use theorizing about Millennial students only as general guidelines, and consider the importance of measured trends and student background characteristics. In order to improve the practical utility of these results, a convenience sample of records was drawn from selected 4-year institutions, which collected data regarding college readiness, student engagement, and college outcomes, and was paired with ACT College Entrance Exams records. A wide range of relationships between high school and 1st-year college activities were measured with only some types of engagement (e.g., religious, sports/fitness, community service) having continuity into the college years. In addition, this study built on the current knowledge about college student outcomes by testing the ability of high school activities and accomplishments to incrementally add to the prediction of 1st-year GPA and 1st-to-2nd-year retention in conjunction with other known cognitive, noncognitive, and college engagement predictors. Using hierarchical linear and logistical regression, number of high school activities was able to capture additional variance in 1st-year GPA, but did not hold predictive utility for 1st-to-2nd-year retention. Hence, student affairs professionals should consider the implications of decreasing high school engagement when both planning for college activities and predicting college student outcomes. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]