In southern California school districts, 8th grade students in history-social science (H-SS) classes did not perform well on the California Standards Test (CST). To improve student performance, middle school H-SS teachers in some districts received staff development in the use of authentic assessment, the understanding and application of multiple intelligences theory, and the application of a student centered focus in lesson design and instruction. The purpose of this comparative pretest/posttest study was to determine if there was significant achievement difference between 2 8th-grade U.S. H-SS classes taught in 2 districts. The research question addressed a significant difference in CST H-SS achievement scores between 8th-grade students taught using multiple intelligences strategies and authentic assessments (n = 28) and those who were taught using traditional strategies and curriculum assessments (n = 31). The theoretical foundation for this study was constructivism. Post-data from archived student scores on the CST H-SS test were collected and analyzed using an analysis of covariance (ANCOVA), controlling for varying differences in CST pre-test H-SS scores. There was a statistically significant difference in posttest CST H-SS scores between the 2 groups (F = 10.491, p < .002), with the nontraditional group scoring higher. Based on the findings, it is recommended that district leaders provide professional development opportunities for teachers in nontraditional constructivist instructional strategies that support student-centered instruction. These endeavors may lead to positive social change if H-SS teachers change instruction and assessment methods to improve student achievement, thus, meeting graduation requirements and enhancing citizenship development.