Why do little girls have to cover their heads? What's wrong with their heads? Why don't boys have to do this?.
OK this is coming from an atheist, let me give a shout to the expert
My understanding is that in Islam both men and women have to dress 'modestly'. The veiling comes from Mohammed's wives being veiled/draped in cloth. There is debate about whether all women should veil because they should aspire to be like a wife of Mohammed or not veil because that is an impossibility.
If you see people on their way to Friday prayers or children going to classes then you will see the boys in baggy clothing and prayer hats.
The clothes men wear in traditional UK culture tend to comply with Islamic ideas of modesty for men, only some omen's clothes do. And hair is something women tend to style and or grow long much more than men.
Some women only wear a veil in the mosque or when praying, some wear it all the time and then there are some, like a student a few years ago who I said to, "you look nice, what have you done different? Is it a new hair do" to which she replied, "No Miss, I' not wearing a veil".
There is also debate about whether the same rules apply to children, children cover their heard in the mosque, a little girl is not a woman but at what point does a girl become a woman? Some people will dress their little girl in a veil, some will expect her to wear one from puberty, some will wonder what has got in to their daughter if she covers her head.
Add to all this, bad hair days and fashion and you have an array of headscarf wearing/not wearing Muslim women and girls.