No, no stereotypes are completely inaccurate. Just like a broken clock is right twice a day. They are, however, all bad. Children, like adults, are complex creatures. Not all boys will react well to a male teacher who gears everything they teach towards a football theme. Nor, indeed, are all male teachers that focused on sports, or acting out depictions of violence. Children need male teachers because they need to see that males can exist in just a wide a range as the women they encounter, and not to fill any percieved lack in the provision of female teachers.