A Headteacher of a school with students from a diverse range of cultural backgrounds said to me that he has students in his class, Muslim girls, who are not allowed to go swimming with the boys. It was a general conversation about kids and their relationship to the body. He emphasised that they are mostly pre-pubescent, being between 8 and 12 years old, implying that sex and sexuality shouldn't matter. Nevertheless, he also teaches sex education to the older year groups.
He said, it's not about religion, it's about power - the fathers control of their girls.
I wonder whether he would have said this had I looked Asian.