The purpose of this study was to examine the relationship between the size of high schools, their percentage of SED (socio-economic disadvantaged) students, and API (academic performance index) scores in California, and determine if teacher preparation is a contributing factor. The 2010 API scores and median income of all 52 counties, and the 2010 API scores and % SED of 1,089 high schools were tabulated and graphed to determine the strength of the correlation between the two different sets of data. Also, the percent proficient levels (in English) for all high school students by grade (9-11) and by socio-economic status from 2003 to 2010 were compared. Lastly, the number and percent of English and math teachers with the proper credentials are presented for analysis. Results indicate there is a strong correlation between the % SED and API of large high schools, and the correlation decreases as the size of high schools decreases. Also, the percent proficient levels in English of SED students are consistently lower than non-SED students across all grades. Results show that the performance of large, high % SED high schools on the CST (California Standards Test) is inferior to their large, low % SED counterparts, regardless of the percentage of teachers holding the proper credentials. Parents, policymakers, educators, and researchers need to question the scope and purpose of high stakes tests if the tests, by design, cannot account for circumstances beyond the control of students, parents, and schools. (Contains 5 graphs.)