Girls vs. Boys in the Classroom

It seems I'm always writing about gender issues, but as a sociology major it's a topic that comes up frequently. I recently observed a class in my practicum school where the teacher separated the boys and girls into opposing teams to review math concepts. The girl's team was named the "Fillies" and the boys were the "Stallions." As we know, boys are generally expected to perform better at math and science than girls. Boys have historically been more likely to pursue fields that incorporate math and science, such as engineering and architecture. The boys were very aggressive and the girls seemed to be pretty laid back. The boys were constantly laughing at the girls if they made a mistake and were determined to win. Is it okay to separate girls and boys for these types of activities? Would they have just as much fun on a team with mixed sexes? By separating them by gender are we further implying that they are different? I'm just concerned with the way we perceive gender in this society and the way we are defining gender to our children.