It's period three and history for class 7RBE. After writing the lesson objective on the board - "to identify key facts about the Crusades" - Miss asks the class to write down what they already know. Then the children take turns reading aloud from the textbook before filling in a Crusades acrostic. The second half of the lesson sees them filling out a worksheet and answering questions from the book.
On one level, it seems innocuous enough. But the Miss handing out the worksheets and helping the class to fill in their acrostic is not a qualified teacher. She is a cover supervisor.
The use of cover supervisors to take a class when regular teachers are absent has provoked a furious debate within the profession. While some see them as the answer to every headteacher's prayers - an effective and cheap alternative to supply teachers - to others they are the thin end of a wedge, diminishing the status of the profession and leading to a time when the idea of a teacher in every class is an anachronism.
The issue will become even more contentious from September, when a new clause in the school workforce agreement will stipulate that teachers should "rarely cover" for sick or absent colleagues, forcing schools either to seek supply staff to plug the gaps or employ a full-time cover supervisor. A school can pay upwards of pound;150 a day for a supply teacher, while cover supervisors typically earn pound;6.50-pound;7 an hour.
At Icknield High School in Luton, cover supervisors start on pound;13,000 a year. Ms Cartmel, the cover manager, who runs a team of five, admits that saving money is one of the main attractions of employing cover supervisors rather than supply teachers. Having a team of cover supervisors on hand also avoids the frantic early morning ring-around to arrange a supply teacher.
But Ms Cartmel insists there are more benefits to having them than cost saving and convenience. "I believe in this system, and I see the benefit to the children," she says.
She argues that because they are based in the school, they are acquainted with policies and procedures and are familiar to the children. Both can be vital when it comes to classroom management.
"The downside of a supply teacher is that they don't know the children, they don't know the school and they don't know the behaviour polices," she says. Children are more likely to play up when they have a supply teacher they don't know than a cover supervisor they do, she suggests.
Icknield High still uses supply teachers. There are some shortages for which cover supervisors are less appropriate, such as practical science lessons, or where long-term cover is needed. "I'm not saying there is no use for supply teachers, but on a daily basis it is better to have a cover supervisor," says Ms Cartmel. "We might have lost an hour of teaching, but we haven't lost any learning."
Key to the success of the system at Icknield High are proper training for cover supervisors and making sure the class is left suitable work, Ms Cartmel says. Teachers who take a planned absence leave a pre-prepared lesson, which the cover supervisor then delivers. When the absence is unplanned, lesson preparation is done in conjunction with the head of department or other qualified staff. Of course, teachers are available in neighbouring classrooms should the supervisor need help.
"It is about making sure we're never just babysitters," Ms Cartmel says. "I agree that we're not teachers and we will never replace teachers, but we do ensure there is a high standard of delivery in the absence of a colleague."
But not everyone is convinced the impact of cover supervisors is so benign. To opponents, their widespread use, and the gradual acceptance that they are part of a school workforce, has significant and potentially worrying implications for the role of teachers in education.
"It is the thin end of the wedge," says Andrew Baisley, an official with the NUT in Camden, north London, and a maths teacher at Haverstock School. "It is undermining the profession and encourages the belief that it is not terribly important to have a teacher in every classroom."
He warns that the pressure on school budgets over the next few years, as the impact of the recession is felt in public spending cuts, will encourage school leaders to look for cheaper alternatives.
"It is a straightforward principle that you should have a teacher in front of every class - but when you break that, you don't know what you're letting yourself in for," Mr Baisley says. "I'm not suggesting this is going to be a rapid transition, but I fear that over the next decade there is going to be a whittling away, and people will look for reasons why we don't need teachers in every class."
Mr Baisley raised concerns at this year's NUT Easter conference about schools appealing for people with military or police backgrounds to become cover supervisors. It also emerged that one school had employed two bouncers. He believes this emphasis on managing behaviour instead of learning is an inevitable result of not having qualified teachers in front of a class.
"If you stick someone unqualified in a classroom, they won't be able to offer the kids any help, so you are setting up conflict," he says. "The only way you can get through that is by being loud and stern."
Guidance from the Training and Development Agency for Schools (TDA) states that cover supervisors should only be used for "short term" absence, but there is no agreement on what constitutes short term.
A debate at the NUT conference called for the use of cover supervisors to be limited to the first three days of absence in secondary schools and a single day in primaries.
While the danger that cover supervisors pose to regular teachers may be hypothetical, the threat to supply teachers is all too real. Every time a cover supervisor takes a class, it is one lesson less for a supply teacher.
Nicky Keller, director of Education Resourcing, a supply agency covering parts of the East Midlands and East Anglia, has heard of schools where cover supervisors have been employed for long-term absence. In one case, a cover supervisor stood in for a technology teacher for three terms. She acknowledges that there are some dedicated and well-trained cover supervisors, but the lack of regulation means not all will meet these standards.
"The kids are losing out if they don't have a specialist, trained person in the classroom, particularly if it is a practical subject such as science or technology," she says.
"Cover supervisors are a good thing because they know the school and they know the system, but the way they are used needs to be monitored better. Local authorities should check what they're covering and how often."
TDA guidance sets out the role of cover supervisors, but the lack of clear demarcation between their job and that of a teacher leads some to perceive a worrying overlap.
Tony Callaghan, a former headteacher and trade union official, set up the group Teachers in Classrooms to campaign against what he sees as the creeping erosion of the position of teachers. He believes cover supervisors frequently trespass into territory that should rightly be the preserve of teachers.
"It's not just a question of supervising a class - some of them are actually teaching," he says. "It is depriving other teachers of work, and if classes are not being taught by a qualified teacher, that is wrong."
The risk of cover supervisors straying into teaching is even greater when a teacher's absence is unplanned, he says. Last-minute absences mean it is likely that the stand-in will be left to rely on their own skills rather than a prepared lesson.
While he recognises that supply teachers vary in quality, and the potential benefits of employing someone familiar with the children, he says heads should be upfront about why they employ cover supervisors. "It is always about money," he says. "Parents are duped into thinking that when a new person appears in the classroom they are a qualified teacher, but headteachers should come clean about this so parents know exactly what is going on."
He predicts that the use of cover supervisors will expand dramatically from this September, when the "rarely cover" rule comes into play. Icknield High, for example, is just one school planning to recruit more cover supervisors for the new school year.
Mr Baisley recognises the irony in opposing the effects of a measure brought in to ease the burden on teachers. He believes this is one reason why the profession has been slow to wake up to the potential threat. "Teachers can see the advantage of not having to cover and they're hesitant about giving that up," he says.
If cover supervisors did eventually spell the end of the idea that every classroom should have a teacher, then Davison High School for Girls could turn out to be school zero. Davison High in Worthing, West Sussex, is thought to be the first in the country to have introduced cover supervisors, in 1998. It now has five on its books, with plans to expand the team from September.
Kay Taylor, assistant head, says the idea behind it was to provide time for teachers to undertake professional development courses. It also means that a teacher's non-contact time is inviolate and not at risk from the need to cover for an absent colleague.
A variation on the dilemma over the "rarely cover" requirement, this captures the difficulties some teachers have over the role of cover supervisors. If schools cannot afford a supply teacher, then a cover supervisor is the only way they can protect non-contact time. If teachers want to preserve their free lessons, then it may be that they have to accept the use of cover supervisors.
Susi English was the first full-time cover supervisor in England. She was appointed at Davison High in 2000 and went full time the following year. Previously a travel agent, she applied for the job to see what it was like at the school where her daughter was a pupil, but says now she loves the variety. "When you come in, you don't know what year group or what subject you're going to cover, but there is a lot of support and training," she says.
Mrs Taylor says that while cover supervisors at Davison High do more than just write up on the board the work the class is expected to do, they stop short of teaching, although she recognises there can be a fine line between teachers and cover supervisors.
"It is not about being a teacher on the cheap: it is about helping the pupils find a way into the work that has been set for them," she says. "They're managing a class, but they aren't teaching."
She believes the use of cover supervisors also encourages pupils to strengthen their independent learning skills, but rejects suggestions that this could make teachers obsolete. "Teachers are absolutely crucial, but the role has changed - we're not the sages on the stage any more," she says. "Children have access to information technology and they don't rely on the teacher to be a knowledge-giver."
She says this shift means it is possible to envisage a situation where a teacher may be responsible for the learning of a group of pupils, but where it is not necessary to have a teacher in every classroom. Cover supervisors may have a greater role in subjects where it is difficult to recruit sufficient teachers, such as English, maths and science.
But could an increasing use of cover supervisors end up putting too much responsibility on their shoulders? Christina McAnea, head of education at Unison, says existing concerns will only be magnified once "rarely cover" comes into operation.
She says cover supervisors are seen as the cheaper option, but employing untrained staff will ultimately affect standards. "Staff are not being trained to the right levels and they're not being paid for the work they do," she says. "Come September, they will be put under increasing pressure to take on additional roles."
In primary schools, for example, it is not feasible to hand out work and expect the children to get on with it, so support staff asked to cover end up taking on more of a teaching role.
"If you have a primary school class for half a day, you are teaching. They are not sitting there with their heads in their books," Ms McAnea says. "Headteachers need to understand the difference between cover and cover supervision."
Although the fear of losing precious non-contact time has muted some of the criticism from teachers, there is still a widespread suspicion about cover supervisors. At Icknield High, Ms Cartmel recalls some difficult meetings with staff when they were introduced. But she believes the mood changed once teachers saw it in practice.
"Nobody wants to do cover - we're helping teachers by doing it," she explains. "Ideally, you would want the teacher in the classroom, but sometimes it is necessary for them to be elsewhere."
Most teachers would agree that, at best, cover supervisors are a pragmatic response to the absence of a regular teacher - saving money and maintaining standards of behaviour. But as their use is increased, the notion that you don't need a teacher at the front of every class could edge towards becoming a worrying reality.