The problem this study addressed is based on research that has shown that students reading below grade level at the end of third-grade are at higher risk of not graduating high school on time with their peers or not graduating high school at all. The purpose of this study was to investigate whether third-grade reading proficiency is an indicator of a student's post-secondary education preparedness. The study focused on answering the following three research questions: (a) Is there a relationship between students' abilities to read at grade level based upon their third-grade end-of-year Gates Reading Assessment and their performance on the reading comprehension component of the ACT? (b) How do students identified as reading below grade level at the end of third-grade, based upon their Gates Reading Assessment, perform in comparison to their peers on the reading comprehension component of the ACT? (c) Is there a relationship between students' abilities to read at grade level by the end of third-grade, based upon their Gates Reading Assessment, and their post-secondary education readiness indicated by ACT College Readiness Scores? A quantitative analysis of the data was performed through t-tests for both dependent and independent means along with a logistic regression. The analysis of these data found statistical evidence of a relationship between student performance on the Gates Assessment and student performance on the ACT. Eighty-nine percent of students who were identified as reading one grade level behind at the end of third-grade did not reach the college readiness benchmark set by ACT. In comparison, 99% of students who were identified as reading at or above grade level by the end of third-grade scored at or above the college readiness benchmark of 21 set by ACT, leading the researcher to believe that third-grade reading proficiency does have an impact on post-secondary readiness. The analysis of the research and data from this study shows that third-grade reading proficiency is an indicator of post-secondary readiness. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]