This study was relational, non-experimental, explanatory, and cross-sectional in nature, using quantitative methods to explain the influence of student, staff, and school independent variables on 6th, 7th , and 8th grade student achievement in both Language Arts and Mathematics on the 2011 NJ ASK. The variable of interest was the length of the instructional day and controlled student, staff, and school variables. This study provides descriptive research on the relationship between the length of the instructional day and other predictor variables and student achievement. The study used approximately 200 schools for each grade level and subject area combination. The percentage of students eligible for free and reduced lunch (%FRL) was found to be the strongest predictor on the 2011 NJ ASK Language Arts and Mathematics for Grades 6, 7, and 8 in this study. Student attendance was also found to be a statistically significant predictor of the percentage of students scoring Proficient and Advanced Proficient on the NJ ASK Language Arts and Mathematics for Grades 6, 7, and 8. There is no statistically significant relationship between the length of the instructional day and the percentage of students Proficient and Advanced Proficient on the NJ ASK Language Arts and Mathematics scores for Grades 6, 7, and 8. [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.]