The purpose of this study was to examine the impact of the length of years of preschool attendance on the academic achievement and retention of third and fourth grade students in high and low achieving schools. The study consisted of the analysis of secondary data, i.e., mathematics and language arts literacy scores as the measurement of academic achievement of third and fourth grade students. The scores were taken from the state's standardized test known as the New Jersey Assessment of Skills and Knowledge (NJ ASK) for third and fourth grade students in both low and high performing schools. Retention, the process in which students are mandated to repeat a grade identified as a non-proficient or failing grade, is also examined. Both retention data and the length of years of preschool attendance were extracted from the accumulation folders of 1,068 students. Students' gender, ethnicity and social economic status were provided via the standardized test as part of the demographic information requirement. The study also compared what the district considered high and low performing schools. The criteria used to determine high or low performing school status was student progress as measured by the NJ ASK test scores and the school's ability to acquire or make Adequate Yearly Progress (AYP), a status mandated by the state of New Jersey Department of Education. Schools with a minimum of 80% of the total student population in all sub-groups (i.e., general education students, special education students, ELL students, ethnicity groups, and socio-economic status groups) identified as proficient and above proficient on the state's standardized test were labeled as high performing schools. Schools that did not meet the minimum required proficiency of 50% of the total student population for two consecutive years were labeled low performing schools. Unfortunately, the district had a high mobility rate which flawed the categorizing of high and low performing schools. The study compared two low performing schools with two high performing schools, and consisted of approximately 1,068 participants with two consecutive years of test scores and retention rates. The study concluded that, in both low performing and high performing schools, students who attended preschool for two years scored significantly higher on the NJ ASK test in language arts literacy and mathematics than students who attended preschool for one year. Students who did not attend preschool scored lower than any other populations. It was further concluded that students who attended two years of preschool were retained less than students who attended preschool for one year, or who did not attend preschool in low performing schools. Students in low performing schools with no years of preschool attendance had the highest retention rate. It was further concluded that regarding hypothesis four, there was not a significant difference in the retention of students in high performing school. The results of this study will be presented at state and national conferences to support the continuous funding for preschool education in the state of New Jersey. It is also the intention of the researcher to use this study in the publishing of articles that advocate for preschool attendance. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]