No matter how fond your memories, the thought of teaching at the school you attended can be unsettling. However long ago you left, the odds are that some of your teachers will still be there - and breaking the habit of calling them Sir or Miss can prove surprisingly difficult.
Of course, the novelty of being allowed inside the staffroom is a big plus point, but talking shop with the biology teacher who once caught you smoking in the toilets can take some getting used to. And if you hold a management position, delegating to the maths teacher who recalls your acute aversion to deadlines can be excruciating.
But Catherine Bourne found that, once the initial awkwardness is over, teaching at your old school can be a rewarding experience. She teaches English at Bennett Memorial diocesan school, a mixed 11-18 comprehensive in Tunbridge Wells, Kent. She thoroughly enjoyed her time at her old school - so much so that she never really left.
"I finished at Bennett in 1994 and started an English degree at Christ Church College in Canterbury," she says. "After I'd finished my degree, I wasn't really sure what I wanted to do, but I'd always thought I might like to try my hand at teaching, so I enrolled on a PGCE course at Christ Church."
But when the details of her first teaching practice arrived in the post, Ms Bourne came in for a big surprise: she found that she had been assigned to her old school.
"At first I was a bit cross," she says. "I'd been assured that this wouldn't happen, but in the end I decided to give it a go. I'd loved my time at the school and the thought of training in a familiar context did feel reassuring."
Initially, there was some confusion to clear up with the students - her Year 13 class felt sure they'd seen her somewhere before. And indeed they had: she had been their head girl when they started as Year 7 pupils. But Ms Bourne's concerns about working with her former teachers were short-lived.
"At first it was a bit weird, but I soon got used to it," she says. "Staff at the school are very professional and treated me accordingly. The school had changed a lot since I'd been a student there - for a start it had changed from being single sex to a mixed-intake school."
As her teaching practice drew to a close, Ms Bourne had to start looking for a suitable position. When a vacancy came up at Bennett, she was unsure whether to apply.
"I worried that attending, training and teaching at the same school would damage my career prospects," she says.
"But at that time I wasn't sure whether teaching would be my long-term career. I felt it was a good school and close to home, so I decided to go for it - initially just for a year."
Five years on, she is still there and very much enjoying the challenge of the additional responsibilities her role as head of Year 11 has brought.
"This is a great school with fantastic students. As long as the job continues to offer me the challenges I am looking for, I'm happy to stay.
"Sometimes I've thought of moving on, but there's no point in changing schools just for the sake of it."
James Williams, PGCE programme convener at the Institution of Education at Sussex university, advises career-minded teachers who do end up teaching at their old school to think carefully about the best time to move on.
"There is a danger that you could spend too much time at one school, and this can make moving to other schools much more difficult as the interview panel will only be able to see one set of experiences," he says.
"A formula I work to is around two to three years in school one, then about five years in school two. It allows you to establish yourself, consolidate your experience, then move on and develop in another setting."
Mr Williams believes the advantages of working at the school you attended as a student can outweigh the advantages.
"You know the school and the system, and they know you," he says. "There should definitely be less fitting in to do. As an old hand in school, you're less likely to make the mistake of sitting in the wrong chair at break time or using the wrong mug."
On the downside, he says a teacher who is a familiar face can more easily be overlooked and be left without the necessary support - especially in the case of newly qualified teachers trying to meet the induction standards. On the flip side, there is also a temptation for colleagues to treat you like a trainee or a student at the school.
For teachers considering a move to the school they attended as a student, Miss Bourne has the following advice. "If you are confident that it's a supportive and professional environment, then go for it. Don't expect everything to be the same as it used to be, but take advantage of what is familiar to you.
"It certainly worked for me."