Approximately 225,000 children from birth to age three are affected by developmental delays, and additionally, 49,000 are affected by a physical disability (U.S. Census Bureau, 2006). Fortunately there are policies and programs that help young children with disabilities achieve positive outcomes in school and live independent lives in the future. Part C of the Individuals with Disabilities Education Act (IDEA), Early Intervention, is a federal program that provides services to infants and toddlers with developmental delays or diagnosed disabilities. Part B of the Act, the preschool special education program, is similar to Part C; however, services are provided to 3-5 year-old children. The study included secondary data analysis to examine the impact of several factors, including the Early Intervention program, demographic factors and potential mediating factors on preschool special education student outcomes. The Pre-elementary Education Longitudinal Study was utilized to answer the following research questions: 1) What is the effect of Part C Early Intervention on the pre-academic achievement of preschool special education students? 2) What factors are related to parent involvement? 3) What is the relationship of parent involvement to the pre-academic achievement of preschool special education students? Linear Mixed Models were used to test the long term effects of Early Intervention and parent involvement on student outcomes and the effect of Early Intervention on parent involvement. Although Early Intervention did not predict parent involvement, results indicated that the program had a positive significant impact on cognitive student outcomes. Children who received EI were more likely to score higher on the cognitive tests including the Woodcock Johnson III: Letter-Word Subtest (p = 0.03), the Woodcock Johnson III: Applied Problems Subtest (p = 0.026), and the Peabody Picture Vocabulary Test (p = 0.04). Furthermore, parent involvement had a significant effect on the Woodcock Johnson III: Letter-Word Subtest (p = 0.019), The Woodcock Johnson III: Applied Problems Subtest (p = 0.000) and the Preschool Kindergarten Behavior Scale-Behavior Subtest (p = 0.014). The impact of parent involvement on behavior increased over time. Implications are that early intervention is effective in increasing cognitive development levels which can lead to positive school outcomes such as higher grade point averages and graduation rates in the future. Since parent involvement appeared to be an important factor in improving student achievement, it was suggested that policies such as IDEA encourage interventionists to work collaboratively with families to help children reach their full potential. [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.]