A small theatre company has accused a private girls' school of discrimination after a teacher asked it to avoid any discussion of gay relationships during a sex education session.
Black Cat Theatre said the request from the teacher at St Margaret's School, which it complied with, was "morally reprehensible".
It also claimed the school in Hampstead, north London, was risking its pupils' health by denying them important safety information.
St Margaret's, where fees are #163;10,000 a year, has confirmed that the request was made following staff concerns about the "edgy" nature of the performance to an audience of 12-15 year-old girls.
But the head said it did teach them about gay relationships elsewhere in the curriculum.
The row blew up when Black Cat visited St Margaret's last month to perform a show as part of a sex and relationship education programme.
Teachers chose not to book the company's show on gay relationships, 'When Larry met Gary'.
But the first module it did opt for, on the dangers of substance and alcohol abuse, culminated in a boy being drugged and raped in a scene which prompted a member of staff to walk out.
The school said: "Knowing that this section had been considered inappropriate by some staff, the PSHE co-ordinator respectfully asked if the next shows, on under-age sexual activity and handling peer pressure to have sex, might avoid gay sex as a topic matter."
Barry Lillie from Black Cat said: "It seemed very odd in this day and age. If you are going to broaden children's minds about sex you have got to talk to them about all different types of sex.
"It is no less important in a girls' school. There are girls that are gay as well as boys. They can come up against the same prejudices and also catch sexually transmitted diseases.
"We were absolutely astounded that a school would potentially puts it pupils in danger."
He said the ban had led the actors to skirt around important issues like HIV and anal sex. No other school had asked for them to leave out material on gay relationships.
Mark Webster, St Margaret's head, who said he was away on the day of the performance, claimed some that parents had expressed concerns in advance of the session.
The teacher who asked for the changes knew that gay relationships would be covered in other parts of the school's PSHE programme.
"Let's not be disingenuous," he said. "It is an area that people have individual viewpoints about and I think her view was that it was best to take a cautious line.
"It was just the sense that this might go somewhere we hadn't bargained for."