You enter the staffroom for some well-earned refreshment to find your favourite mug has been consigned to that pile of anonymous crockery kept for unsavoury-looking supply teachers. Or the label on your pigeonhole has been torn off in readiness for that ruddy-faced NQT who's just been whisked around your classroom without so much as a by-your-leave. Come to think of it, why doesn't the cleaner stop to chinwag any more? To put the tin lid on it, that in-service training you discussed with the head some months ago has been offered to A.N. Other, when everybody knows that Delaying Tactics for Middle Managers has always been your thing.
Your problem, as if you needed reminding, is post-resignation blues - and teachers across the country who have just resigned are finding out the hard way that it can be the meanest blues of all.
"Serving out my notice in my last job was the most appalling time," says Alice Stafford, an art teacher now an artist-in-residence and freelance trainer. "I felt so desperate and isolated at times that I even started to smuggle my cat into school in my handbag .
"As soon as the resignation letter goes in, it's as if you suddenly become an unperson who no longer has any validity. I was suddenly frozen out of anything that mattered, and was constantly asked to do all kinds of extras. In a situation like that, it becomes so hard to do your best."
Joanne Pearson agrees. She is serving out her notice, having recently landed a new teaching job abroad for September.
"I've noticed a change in attitude from the head and deputy since I resigned," she says. "Some teachers seem to envy the fact that I've escaped.
"It's the little things you notice - like not being backed up on behaviour issues, and all sorts of petty things that make you uncomfortable in your day-to-day work. It makes it hard to stay motivated... I'll be glad to see the back of this place."
These are not isolated instances. Others complain of being made to feel "disloyal" for leaving, of having funding withdrawn for night-school degrees, of bloody-mindedness over references, withdrawal of non-contact time, or dwindling levels of additional support in the classroom.
John Howson, the TES columnist and expert on teacher employment, says that in the summer term some 24,000 teachers will be serving out their notice in the UK. You don't have to be Einstein to work out that even if only a minority are having a rough time in this educational twilight zone, this negative psychology could be making a sizeable impact on the profession.
One of the biggest obstacles to a cure for post-resignation blues is that the problem is not widely acknowledged. Certainly, the teaching unions appear to be unaware of it, offering at best a knee-jerk response, at worst oblivion or outright refusal to comment.
"If any of our members were discriminated against, we would act on their behalf," says Olive Forsyth, of the National Union of Teachers.
Russell Clarke, deputy general secretary of the Secondary Heads Association, denies the phenomenon exists. "Most members of staff who move on do so with the full support of their headteachers and colleagues," he says.
Maybe. But Nuala Pettifer, an experienced teacher who now works as an adviser on equal opportunities in schools, is not so hard to convince.
"Teachers serving notice tend to lose out on what's now called continuous professional development, which all teachers are entitled to," she says. "Staff are often made to feel like persona non grata. Sometimes they're expected to do more than their fair share of playground duties or assemblies, but lose out when it comes to special events, trips, or even training opportunities.
"In such a time of limbo, I think most people just want to keep their heads down and get through it. If they're on the way out soon, the last thing they want to do is to make a fuss. But I have to say that in my experience schools are ideal breeding grounds for some of the most flagrant abuses of equal opportunities - because so much power is invested in one person: the headteacher."
Predictably, it is in the private sector that the negative psychology of the notice period appears to have been seriously considered. Paul Taffinder is a partner at Accenture, an international management consultancy that has used psychological and anthropological models to develop a better understanding of relationships and dynamics in the workplace.
"Very often, a person who hands in notice has resigned mentally a long time before that, so the notice ends up being much longer than the official period," he says. "If you are part of a school, then you are part of a tribe and you plough your energies into enhancing the interests of that tribe - it's part of the survival instinct.
"If somebody in my department were serving out notice, I would know that their interest was going to be elsewhere. Ideally, I would want to accelerate this process, although this option is often not available to people working in the public sector."
He agrees that the sense of dislocation that ensues while under notice is bound to have a detrimental effect. "It's hard to say how this might affect individual children, but I think it is bound to have a significant impact on a profession that is already overstretched," he says.
Tribal instincts apart, Mr Taffinder is far from resigned to the inevitability of post-resignation blues, although he believes that "more open-minded forms of leadership" would be needed in order to counteract their highly demoralising effects.
"If you deny the availability of new knowledge, then you deny new options for action," he says. "And it makes no sense to deny the opportunity to talk about this phenomenon in the public domain when there could be a very productive debate about it."
Names of the teachers in this article have been changed