Two typical phenomena in elementary school level have been identified; the majority of teachers are females and the girls are superior to boys in school achievement. This study was purposed to investigate the relationship between the sex differences in elementary school children´s achievement and the sex differences of teachers. Six classes of fourth, fifth, and sixth grades, half by woman teachers and half by woman teachers, were used. The data analyzed were children´s achievement scores tested by an achievement motivation test, academic scores in Chinese and arithmetic, self-reported learning experiences, and scores based on a survey of teachers´ attitude toward their students. The last datum was collected from 32 woman teachers and 31 man teachers included other classes in other grades. The results indicated that although the sex differences in achievements were significant, the differences were not related to sex differences of teachers. In the respect of teachers´ attitudes toward their students, however, the boys and girls were evaluated differently by their teachers. The main findings in this respect were (I) Teachers believed that the students of their same sex were more influenced by their own behavior models. (2) The traditional favorable characters of so-called good student were more frequently assigned to girls rather than boys. (3) The boys were highly expected to achieve, but the teachers were also more disappointed by boy students´ failure. (4) Boys were frequently evaluated as the classroom trouble makers, and hence they were frequently punished than girls. These facts might be thought as the causes of male students encountering more social and elementary school than their fellow female students.