What is the difference between a blouse and a top? Is it ever acceptable for all women teachers to bare their midriffs? Does forcing a male teacher to wear a tie constitute sexual discrimination? Such are the dilemmas as more and more schools introduce a dress code for teachers, the subject of approving letters in The Daily Telegraph.

But while heads say it is setting a good example, teachers are complaining of being told off by pupils for not being properly dressed. And, it is understood, at least two women teachers have been sent home to change - one for wearing a top deemed to show too much flesh, the other for her shoes.

For Mike Griffiths, a dress code for teachers is a question of consistency.

His is a fairly traditional school, with a uniform of school blazer and tie, white shirt and charcoal or black trousers. Sixth formers have no set uniform but are expected to adhere to an “office dress“code of shirt and tie with jacket optional. And if sixth formers have to stick to it, then so do the staff. “We believe that if people are looking smart and well ordered, then the learning is a bit sharper,” Mike says. “If we believe it is important for the students, then surely the same applies to the staff.

It would be unreasonable to expect the students to adhere to a higher standard than the staff.”

Mike introduced the dress code for staff at Northampton School for Boys, a state secondary, about three years ago. Although it does not stipulate a uniform as such, for men it means a shirt and tie, for women a blouse, with Mike, as headteacher, having the final say in interpreting the code.

“We are role models and if we expect the students to behave in a particular way we should do the same. We feel the dress code helps us establish an ethos and attitude to learning,” he says.

Although there is no record of how many schools have a dress code for their staff, there are signs it is becoming increasingly common. One teacher in the West Midlands, who asked for her inner city school not to be identified, says when a uniform including blazers was introduced for the pupils, staff were told they had to wear jackets. “I can understand that and I’m happy to wear a jacket, but when they started saying we could not wear a jumper or cardigan underneath it I thought it was over the top,” she says.

“We are told we should have a jacket with us at all times when we are walking around school. It feels like we are being treated on the same level as the children.”

She says teachers have been stopped in the corridors and asked why they were wearing a jumper or why they weren’t wearing their jacket, and she knows of two teachers who have been sent home to change. “It has got to the point where the children notice we have been told off and ask why we are not wearing our jackets,” she says. “They don’t trust us to dress ourselves in a manner befitting someone who is going to teach. It is fine to give out a guideline of what is suitable, but another thing to stipulate what we can and cannot wear.”

Last summer, the management team at Walthamstow Academy in east London told local union officials they intended to introduce a dress code for staff when the school opened last September.

Rinaldo Frezzato, National Union of Teachers branch secretary for Waltham Forest, says the code stipulated ties for men, but managers agreed to rewrite it in the face of opposition from staff.

The union is still waiting to see the redrafted code. “It is perfectly reasonable to expect people to dress professionally, but it is unreasonable to lay down particular items of clothing,” Rinaldo says.

“I do not think anybody believes in 2007 that in order to look professional you have to be wearing collars and ties. You should rely on professionals to be professional before you impose rules.”

A spokesman for the United Learning Trust, the Christian charity that runs Walthamstow Academy, says there is no standard policy across its nine existing academies on staff dress codes.

“Students in our academies report that they value their own uniform and they appreciate the fact that their teachers also look smart,” he adds.

“Some academy principals have decided that it is helpful for staff to have guidelines as to what might constitute professional attire. This policy is to be discussed fully with professional associations and will develop in consultation with academy staff at a local level.”

Malcolm Smith, the headteacher of Whitehaven School in Cumbria, is considering whether to tighten his school’s existing policy - that staff should dress with a degree of formality appropriate to a school where the children wear a strict uniform.

“That is open to interpretation and I am talking to colleagues about whether or not that needs to be clarified,” he says. “I have had one or two complaints from pupils and parent governors, asking why should children wear a uniform when teachers are coming to school in jeans.”

No decision has yet been made but the discussion has revealed strong views on both sides. “There are two quite clear camps,” says Malcolm. “Those who enjoy the freedom to express themselves with their clothes and those who say teaching is a profession and we should be dressing professionally.

“There is a bit of unfairness in asking children to conform to a uniform if we do not maintain a reasonable level of dress ourselves, but there is also the view that when you look at other professions, such as doctors and so on, they are not all dressed up as they were 20 years ago.”

David Snashell introduced a dress code as head of Cowes High School on the Isle of Wight when he arrived three years ago. “I wanted a clear standard of professional behaviour as an example to pupils. Teachers are professionals and there are conventions and standards of dress that go with that, and that is the message you are sending,” he says.

The dress code forms part of the staff handbook and reads: “Staff are expected to dress in keeping with their professional status and as a good example of a professional to students and visitors. Staff should be neat, smart and tidy, wearing clothes which are commensurate with their post in the school. Teaching staff dress is expected to be formal rather than casual.”

“I don’t want uniformity,” David says, “but I expect the majority of my male staff to wear a tie, or at least a properly collared shirt if it gets warm. People know what to expect and respect that.”

He says senior staff will have a quiet word with teachers who are thought to be dressed inappropriately. “Just a gentle reminder is all we have ever had to do.”

Mike Griffiths says he has not yet had an instance of staff turning up improperly dressed, but in the first instance this would be dealt with by means of a quiet discussion. “We occasionally have issues with staff on supply, who may come here and dress less formally than we would expect, but some then ask to borrow a tie because they feel like a fish out of water,”

he says.

“When you come for interview here it is obvious what the ethos is. The formality suits us. A degree of order and routine is something that is useful.”