The purpose for this correlational, cross-sectional, explanatory was to explain the influence of the length of the school day on the total percentage of students who scored Proficient or Advanced Proficient (TPAP) on the New Jersey Ask (NJ ASK) in Language Arts and Mathematics in Grades 6-8 in for student populations with low, median, and high socio-economic status who attended schools with below average, average, and above average school day lengths. The data analyzed included the length of the school day with controlled student, staff, and school variables. The results from the study serve to distinguish how this intervention influences TPAP based upon socioeconomic status (SES). The study used over 600 public schools for each grade level/subject combination. For all grade level/subject combinations, socioeconomic status (SES) by far had the largest predictive contribution to the dependent variable compared to the other predictor variables.