S.O.
Is he bothered by it? If not and you like the school, I say no. My daughter's best friend (now 8) is a boy and they have played together beautifully since infancy. He is very comfortable with girls in his school class as a result too. I would say it's only a problem if he says it is... ie they don't have any boy stuff to do and I don't like the girl stuff they always do. In a school environment he will actually benefit some as he will learn "girl skills" of communicating more and negotiating more. If you feel it's affecting him negatively, then move him. But most teachers are very sensitive to individual kids needs and styles and at that age, he will likely be fine and even benefit.