Emma Wright, 37, who teaches at Streatham and Clapham high school, in south London, took off her clothes for the Channel 4 series, How To Look Good Naked.
Photos of Miss Wright posing nude were even projected on to the side of Waterloo station.
A spokeswoman for the Girls' Day School Trust, which owns the prep school where Miss Wright works, said she told the headteacher that she was appearing on the show and had taken part only in a personal capacity.
However, the school will now be asked to explain itself when the new term starts in September.
While some parents supported Miss Wright's decision to take part in the programme, saying it did not affect her performance in the classroom, others were critical that she had taken time off during the term to do so.
Marzena Scanlan, whose eight-year-old daughter is taught by Miss Wright, told the Evening Standard: "We knew she was doing the programme. She had bad dress sense and wore very unflattering stuff. Featuring naked on TV may not be the best thing from a career point of view but it's nothing to distract her from being a good teacher."
However, Christine Di Ahna, whose daughter is also in Miss Wright's class, told the paper: "She took two weeks off, during which the children had to have a supply teacher. She should have done it in her own time."
The programme, presented by stylist Gok Wan, aims to show women how to look and feel better without resorting to plastic surgery. It attracts around 3.4 million viewers a week.
A spokeswoman for the Girls' Day School Trust said: "We are interested in anything that may affect one of our schools and its standing in the community.
"We will discuss the programme with the school once people are back from their summer break.
"Miss Wright has taken part in this programme in a personal capacity.
"It is a series made by a reputable production company for a national broadcaster, to be shown before the 9pm watershed.
"As it is shown before 9pm I do not imagine it would make uncomfortable viewing for young people.
"I understand that the programme was around the all-important issue of women's self-confidence and learning to value themselves and these are issues which we would support wholeheartedly."