The purpose of this study was to determine whether integrating chemistry and mathematics curricula and teaching practices significantly improves academic achievement in chemistry among high school students in Southern California. The study was conducted during the 2008–2009 academic year. A quasi-experimental research design was used to explore the effects of a standards-based integrated chemistry and mathematics curriculum (Integrated CHEMAT) and teaching practices on student academic achievement when compared to a traditional standards-based chemistry curriculum (Regular CHEM) and teaching practices. Academic achievement was based on a researcher-created Chemistry Achievement Assessment (CHAAS). The sample population involved in the research included 136 high school chemistry students attending high school in a Southern California rural school district. The research involved 2 groups of 68 students each: the experimental group and the control group. The data were analyzed using SPSS independent samples t-test, one-way multivariate analysis of covariance (MANCOVA), and profile analysis. Statistical significance was determined at the .05 and .001 levels. Significant differences were found when analyzing the effects of the standards-based integrated chemistry and mathematics curriculum and teaching practices. All 3 statistical analysis procedures (the independent samples t-test, MANCOVA, and profile analysis) indicated that students in the integrated CHEMAT program scored significantly higher than the students in the regular CHEM program in achievement scores based on the results of the CHAAS.