As-salamu `alaykum.
Thank you for entrusting us with your problem. We ask Allah Most High to give us knowledge and guidance and give us patience and to relieve you and all Muslims from their problems.
First, bullying is normal behavior amongst children at any school; as a matter of fact, we all have experienced bullying to some degree. However, we can't afford to ignore it as it may be carried slightly too far with people of different race, color, or culture.
Second, I understood from the question that your son does not mingle with girls at all, he does not talk to them. We have to make a very important distinction between the motives behind this at such a young age. If this arises purely from his not being willing to talk to girls in his classroom, then you should handle this by explaining that a girl pupil is as boy pupil within the classroom context.
He should talk to them and engage in activities involving both boys and girls. At this age there is no harm in him taking part in activities with girls. If, however, this phenomenon is a result of your directions, then let me tell you that you will need to change these directions—your son needs to treat boys and girls equally in school.
At his age, he needs to play with his classmates normally, with no differentiation between boys or girls. Also, any over-protection from dealing with girls may result in quite the opposite effect: as a teenager, he could have many girlfriends or he may become incapable of having any interaction with females.
Let me try to set a precedent with the educational law and guidelines in the United Kingdom and you may then try to take advantage of any similarity at your end. Parents have the right to raise issues related to school with their children's teacher; then, if the teacher does not solve the problem satisfactorily, the parents can approach the head teacher. If this fails to provide a solution, they can raise a complaint to the OFSTED (Office of Standards of Education), who will investigate the matter and act accordingly.
I advise you to start with his school and try to discuss the issues your son is facing with his teacher, then his head teacher, then, if necessary, the local educational authority. This measure should be the last resort for you to take after trying the following avenues:
1.Get closer to the problem. Try to get involved with his educational process by offering to help in his school on a voluntary basis. (It is highly encouraged in the United Kingdom for parents to volunteer at their children's schools.) Your presence in his school will play a vital role on several fronts: You will be able to analyze his behavior, and others, very closely, and thus understand where things are going wrong. Additionally, seeing you as one of the teachers in his school will give your son a sense of security and confidence.
You will create good relations with other parents and that will allow you to pick potential friends that he can invite over after school for play or study (and vice versa). This will all contribute to your son integrating in the school and consequently lessen the ill feelings that other boys have towards him.
2.You need to support him as he goes through this period of distress. Tell him whilst his best friends should be boys because he is a Muslim, he should not shy away from dealing and interacting with the girls in his class.
Point out to him that those who call him gay don't have someone explaining to them what is right and what is wrong, because they are not Muslims.
You can also give him an example with pets: If he has a well brought-up cat at home, it will not behave in the same manner as a wild street cat.
You and his father should ask him to be strong in the face of whoever bullies him. Tell him that if he stands up once they will probably never try again with him.
Give him examples from real life and from the stories of the Companions of Prophet Muhammad (peace and blessings be upon him).
Finally, I encourage you to keep in touch with us and please don't hesitate to ask further questions.