Educational aspiration is one of the most important factors influencing an individual's educational attainment. Although students' aspirations are changeable and the stability of their aspirations is important for their goal reaching, previous studies are rather limited in their ability to capture aspiration changes due to their incomplete findings and methodological limitations. To fill in this gap, this study examined individual educational aspiration changes at a critical period of time when the students were in the transition from high school to college or employment by using a national representative sample of students from the Education Longitudinal Study of 2002 (ELS: 2002). More importantly, it identified heterogeneity through the change trajectories by combining the investigation with a comprehensive list of predictors and consequences such as individual factors, socio-psychological factors, social environmental factors, and prominent college enrollment patterns, and also tested the association between the group heterogeneity with a variety of factors and with the enrollment patterns by utilizing several longitudinal data analysis methods such as Latent Growth Curve Modeling (LGCM), Latent Class Growth Modeling (LCGM), and Growth Mixture Modeling (GMM), and also logistic regressions. Using Latent Growth Curve Modeling, the study found a downward trend in the sophomore cohort's educational aspirations which started with fairly high educational aspirations (e.g. between "Graduate from college" and "Obtain Master's degree or equivalent") at the first time point in the 10th grade and then the aspirations deceased over the next two assessment periods. At the same time, about 80% of the changes took place between the first two assessment periods and about 20% of the changes took place between the second and the third assessment period. Using Latent Class Growth Modeling and Growth Mixture Modeling, the study identified four latent classes among the aspirations change trajectories. According to the shape of their change trajectories, the four latent classes were named as the Mid-Increase class, Mid-Reduction class, Low-Increase class, and High-Reduction class. Logistic regressions results revealed that different sets of factors played different roles in differentiating the different classes. The odds of attempting a higher level of education and being a standard enrollee are higher for the High-Reduction and the Mid-Increase classes and lower for the Mid-Reduction and the Low-Increase classes. As a result, this study has several theoretical and practical implications. It expanded our knowledge of aspiration changes during the critical transition years from high school to beyond and it filled the gap in the current educational aspiration theories. It demonstrated the importance of keeping high and stable educational aspirations during the critical transition years. At the same time, better-fitting educational policies were also suggested to help adjust the relevant factors across all K-16 levels and facilitate different subpopulations of students in response to their unique situations. Study limitations and directions for future studies were also included. [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.]