Most of us accept that, however daunting, the interview is a necessary part of the job selection process. But it has become . She feels you can tell a lot more from observing someone in the class in terms of their manner, the resources used and the practical application of their plans than is evident at interview.

Many heads echo this sentiment, pointing out that by watching a teacher you quickly pick up on their individual teaching style and rapport with the pupils. Sue Riddle-Hart, headteacher at John Stainer community school in Lewisham, south London, says you can soon spot a good teacher by their questioning techniques and the way they involve the children. She would expect a competent teacher to be able to identify the nature of the class and the specific needs of individual children during the lesson, and then address these accordingly.

But Dee McAllister, of Caterham high school, says this is not necessarily true.

“If you want to know what a teacher can do, refer to the performance management information from their previous school,” she says. “It’s not a realistic situation when we’re asking someone with no prior knowledge of the children, their prior attainment, special needs and English language status to deliver a purposeful lesson. The children know that. It’s particularly unfair on NQTs who have not developed their classroom management skills.”

Some teachers’ experiences bear this out. I’ve heard many accounts of teachers being demoralised after delivering an interview lesson to “the class from hell”. One deputy head recalls an exceptionally difficult class.

“I just had to keep going. The only good thing was that, on reaching the end of the lesson, the children did actually demonstrate that they’d grasped the teaching point.”

At Kingsdale school in south London, the lesson, which is the initial stage of the selection process, is seen as a two-way process. Managers there feel it is an opportunity for the candidate to see if it is the right school for them as well as demonstrating their suitability for the post.

But what if a school doesn’t play fair? One teacher told how, after teaching a sample lesson to a class of perfect pupils, she discovered that the class she had inherited was a real nightmare. Certain characters had miraculously disappeared during the interview lesson. It does not necessarily follow, either, that the class you take at interview stage will be the one you teach in post.

One point everyone agrees on is the importance of trained observers who can give constructive feedback that is professionally useful. One teacher said school governors are not generally knowledgeable enough to pick up on the teaching and learning points. At Kingsdale, two senior members of staff observe using a proforma to check the required criteria. They feel this ensures fairness and is the basis for feedback. It also means that the candidate is fully observed, even if one staff member is called away. I did hear of one justifiably angry teacher who, on delivering his carefully planned lesson, was only observed for the closing five minutes.

Most teachers I spoke to felt that the most valid observations were those where they were seen teaching their own class. But this is not always practicable. It is also more difficult when appointing newly qualified staff. It also relies on the candidate’s school accommodating you.

And what if you’re applying for a post in your current school? Rebecca remembers feeling very dejected when she was asked to deliver an interview lesson at the school she’d been teaching in for seven months.

“They’d seen me teach on numerous occasions - it was unnecessarily stressful and showed a lack of faith in my ability,” she said. Even so, she got the job. The counter-argument would be that such procedures must be seen to be fair.

Virginia Hunt is a teacher in John Stainer school in Lewisham, south London