Research indicated that English language proficiency may influence student performance, and that standardized assessments may be biased against students who have limited English proficiency (LEP). This study investigated the influence of language on student performance differences in reading and mathematics. The content area of reading was selected because assessment of performance is necessarily affected by students' language background and English language proficiency. Mathematics was selected because assessment performance may not be affected by the demand for English language proficiency. Research questions examined the performance differences in mathematics and reading scores between students who were identified as LEP and general education students who were labeled proficient in English (non-LEP). Student performance varied between LEP and non-LEP. LEP mathematics scores indicate a higher level of "over achievement" in mathematics above reading scores when compared to the reading and mathematics scores of non-LEP students; this is especially true of calculation type mathematics problems versus word type mathematics problems. An appendix includes assessment data for grades 3, 5, and 7. (KFT)