This study was conducted to explore the impact of teacher ideology on student performance. A definition of teacher ideology was drawn from the pupil control ideology, PCI, created by Willower, Eidell and Hoy (1967). Research concerned with teacher ideology has suggested that there is a definite difference between the custodial ideology and the humanistic ideology (Gaffney, 1997). In particular, the custodial teacher views rules and regulations as a priority, while the humanistic teacher views the student as the priority. Factors which influenced student achievement, such as socioeconomic status, ethnicity, and behavior in relation to how teacher ideology affects student performance were investigated. More specifically, the researcher investigated whether teacher ideology had any effect on student achievement of the entire student body, on student achievement of economically disadvantaged students, and on student achievement of non-white students. In addition to achievement, the effect of teacher ideology on student behavior was also investigated. A slightly positive relationship was found between teacher ideology as indicated by the PCI score, and the percentage of students making learning gains. This learning gain was evident in mathematics scores for all students, economically disadvantaged students, and non-white students. A learning gain was only evident among non-white students in reading. The results demonstrated the need for professional development on teacher ideology and its effects. This study has also indicated the need for further research into iv the effects of teacher ideology on classroom management and teaching styles. The researcher determined that due to a limited number of responses, further research is needed.