Background: Recent decades have been marked by an extensive movement to analyze bias in people's thinking, especially in gender-related issues. Studies have addressed the question of gender bias in classrooms on different levels--the use of gender in books, learning opportunities determined by students' gender, or teachers' gender preferences. Purpose: In this study, we aim to answer the question of whether and under which circumstances the interaction between teacher gender and student gender positively or negatively influences teachers' evaluations of students' performance, while controlling for objective measures of students' performance. For instance, it could be possible that a teacher with the same gender as a student evaluates the student as better than opposite-gender students, independent of their objective performance. Sample: The sample consisted of n > 1,500 Finnish 6th grade students ("M"age= 12.67) and their respective class teachers. Design and methods: Students completed several academic skills tests, including a mathematical thinking test, reading comprehension test, and scientific reasoning test. Furthermore, teachers provided their evaluation of each student, evaluating students' performance in different school subjects and answering questions regarding their probability of academic success. To test whether the teacher-student gender interaction had an effect on the criterion variable, i.e. teachers' evaluation of the students' performance, multilevel analyses accounting for between- and within-class effects were applied. Thereby, the effect of students' objective performance on teachers' evaluation of the students and main effects of gender were controlled for as covariates. Results: The main results indicated that the interaction between student and teacher gender did not influence teachers' evaluation of the students. However, regardless of their gender, teachers tended to evaluate girls as better than boys in first language performance (i.e. Finnish language) and potential for success in school. Teacher gender did not influence the evaluation. Conclusions: The results of the study suggest that the interaction between teacher and student gender is unlikely to be a source of possible bias in the evaluations of students in the Finnish educational system.