A large literature establishes that boys and girls are treated differently in the classroom. Research suggests that this treatment depends upon the gender of the teacher. Using a large data set that observes a matched teacher/student sample over multiple years, this paper explores the impact of teacher and student gender differences on standardized test scores. Three notable findings are found: 1) conditional upon their test scores at the end of third grade, boys perform worse and gain less on math, reading, and writing during the 4th grade; 2) regardless of gender, students of male teachers perform worse than students of female teachers and; 3) there is no significant differential impact of male teachers on boys versus girls--both do equally poorly relative to students of female teachers. These findings cast doubt on the argument that teachers instruct students differentially based upon student gender. (Contains 3 tables.)