Over the past 2 years, almost 45% of the students attending a local suburban high school failed Algebra 2. The purpose of this study was to compare the impact of a cooperative instructional technique (student teams-achievement divisions [STAD]) to traditional instructional methods on performance in high school algebra. Motivational and cognitive theories of cooperative learning constituted the theoretical framework. Motivational theory stipulates that the success of a group depends on the success of the students working together as a group; developmental theory suggests that when completing tasks, students' team interactions increase their mastery of critical concepts. This study focused on whether students' performance in algebra improved when taught algebraic concepts using STAD versus traditional methods. A sequential, explanatory, mixed methods design was used. The treatment group (n = 54) was taught using the STAD cooperative learning technique, and the control group (n = 47) was taught using traditional methods. The quantitative data came from the school-administered end-of-chapter test. The quantitative data were analyzed using ANOVA. Qualitative interview data responses were coded and analyzed using open coding. The findings showed that although students performed significantly higher using STAD, teachers preferred traditional methods because they were familiar with them and they required less planning time. The results suggested that with ongoing training and support, teachers will feel more comfortable using STAD. The study contributes to positive social change by providing teachers with a better understanding of a promising method of algebraic learning that can lead to success in higher level high school mathematics courses. [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/en-US/products/dissertations/individuals.shtml.]