It's that time of year again when seasonal bugs and freezing playground duty add nature's contribution to the year-round pressures of the job. To the joys of a curriculum-heavy term add parent consultations and Christmas productions and its unsurprising that this season sees the highest number of teacher absences in the year. Figures show that each teacher this year has taken on average eight days of sickness absence. Although this is an improvement on past years, when it hovered between nine and ten days per employee, sickness is still costing about schools almost Pounds 1,000 a year per staff member.
For leaders, it has to be one of the most frustrating problems - with a negative impact not only on budgets but on pupils and learning. Behaviour is disrupted and quality of teaching affected.
What should leaders be doing at least to manage illness and reduce its impact?
Academics who study stress and wellbeing in the workplace recognise that teacher sickness comes with the job, but they believe school leaders play a crucial role in minimising or exacerbating its effects.
Constant pressure leaves the immune system weaker and more liable to succumb to bugs, but if it was simply this, City stockbrokers would beat teachers in the illness stakes hands down. It's the combination of constant, low-level stress, long stretches of intense work between holidays, physical exhaustion and operating in a stew of infectious micro-organisms spread by hundreds of children that proves such a toxic cocktail, the experts say.
"That teacher absence rates are higher than the general population is unsurprising - there is a real issue around the intense term structure that can't be overcome," says Professor Peter Earley, of the Institute of Education's London Leadership Centre. But, he says, the ethos of a school, and the quality of its leadership, makes a huge difference.
"Teachers will drag themselves in if there is a collegiate quality to the workplace," he says. "They do not absent themselves lightly, so looking at how absence patterns vary among schools is very interesting.
One might expect this esprit de corps - more like Dunkirk spirit in the dark of a snowy December morning with a list of after-school activities looming - to be found more readily in small schools where staff have closer relations with their colleagues and there is less cover available in the system; in other words, it's more likely to be found in primaries than secondaries.
According to Professor Cary Cooper, a social scientist at Lancaster University Business School, the leader of a small school can certainly nurture a team spirit whereby colleagues provide mutual support and backup. "Where there is a feeling of wellbeing, the impact on illness is noticeable. Government recognises that one of the causes of ill-health is lack of social skills in managers," he says.
The bottom line, however, is that illness will happen, even in the happiest schools. When it does, its impact will largely depend on how well it has been planned for.
This is where the larger school, with in-house cover supervisors - usually recruited from classroom assistants or other non-teaching staff familiar both to pupils and with the ethos of the school - has an easier time of it.
Mick Brookes, the general secretary of the National Association of Head Teachers, says using staff to cover for colleagues simply puts more pressure on those who are not yet sick and can make it harder for the invalid to relax and take the time needed to recover.
"Undoubtedly, the best option is to make sure there are robust systems in place - have spare staff for in-house cover, or, if it's a small school, an arrangement could be made with other schools in the cluster to ensure there is absence cover between them," he says.
Scrabbling around for cover among staff will, in any case, be almost impossible next September, when the "rarely cover" workforce agreement comes in, reducing the 22 hours teachers are supposed to cover for each other to none at all, other than in emergencies.
Better to plan now, says Mr Brookes. "The best mindset is to assume people will be absent and budget for it," he says.
But it's not just a question of ring-fencing money. Supply agencies are the least cost-effective way of dealing with staff sickness. They carry the risk that a tricky Year 9 class will descend into chaos in the hands of newcomer.
"The quality of cover is a big issue," says Mr Brookes. "There is nothing worse than someone who can't keep order."
Back at the Institute of Education, Professor Earley comments: "Looking at the quality of pupils' learning through staff absence is more and more important. There is something very helpful in the familiarity of known staff in the classroom - and it's reassuring to the teachers who are off sick."
When it comes to getting those teachers back to school as quickly as possible, sickness insurance, which provides private health cover, is an option growing in popularity, according to the Schools Advisory Service, the independent schools insurance provider.
Heads that use it say it adds to that feeling of wellbeing that contributes to keeping staff happy and healthy in the first place.
"With this we can tangibly demonstrate that we care about staff welfare," says Richard Schofield, head of Redbridge Community School, an 11-16 comprehensive in Southampton.
The scheme, paid for by the school, not only has a morale-boosting purpose, but a harder-nosed benefit - because private cover means staff are fast-tracked from GP diagnosis to treatment so they are likely to be feeling better and back at work more quickly.
Despite being in a tough area and dealing with challenging children, Redbridge School has very little staff absence and an "outstanding" rating from Ofsted.
All this talk of looking after staff, and taking responsibility for their teachers' health begs one final question: Who looks after the leaders?
Mick Brookes makes a plea for heads to stop being "the most expensive supply teacher in the book". He says that primary heads, particularly, are too often forced to cover for their staff. It shouldn't happen.
"Good leadership ensures contingency," he says.
Back in Southampton, however, Richard Schofield says he is happy to cover occasionally, to give his staff a break.
But who looks after him? "My governors," he says. "One was in this morning asking how I was. That support is invaluable."
FLU JAB IS A DOUBLE WINNER
Fiona Hammond has cut sickness among her staff at Banbury School with a two-pronged, pre-emptive strike.
The school, a large comprehensive in Oxfordshire, offers all its teaching staff free flu jabs every autumn. The programme costs Pounds 1,000 but has paid for itself over the four years it has been running.
Together with "light" weeks - two weeks in December and one in February where Dr Hammond, the principal, has scrapped all after-school events to ease the pressure on her teachers - plus workforce remodelling, the school has managed to reduce days off for sickness by 10 per cent.
"We looked at when teachers' absence was highest and saw it was in the last week of November, the first week of December and the first week of February, so we decided to give the teachers a bit of breathing space in those periods," says Dr Hammond.
She says that her staff has heavy parents' meeting commitments earlier in the autumn term. Although cancelling the Christmas productions would ease the workload, they also play an important part in lifting spirits at the end of term. This system provides a week to catch up on day-to-day teaching free of extra demands.
She has also built up a team of cover supervisors from people already known to the school, including former pupils, so that when sickness does occur it doesn't cause major disruption.
"The flu jab, which is completely voluntary, makes it more convenient for staff to get protection, without having to go to a GP. But it is also true that it's a double winner for the school - if you have the injection, you don't dare be off with flu, and even more so if you've chosen not to have it!"