The rain beats down as you scurry across the car park, slowed down by the bag of marking you didn't complete last night, hoping desperately that some scholar in Year 10 hasn't maliciously locked the front door of the school as a jolly jape. A wet day in school is not likely to put a spring in your step.
We are the mercy of the weather. No matter how sophisticated we think we are, our days can so easily be shaped by the wind, rain and snow. Inspections, budget plans count for nothing. Suddenly your day is in crisis.
When it rains heavily, the drains can't cope. When the school was built, the contractors washed unused cement away, where it still lurks, unreachable.
Now, 40 years later, areas of the school still flood. The drains are overwhelmed, and so are the caretakers. They would be just as effective if they tried to mop up the sea.
The school seems too small. Children form groups in corners. They are bored and fractious. They lean against each other, pushing, teasing and arguing.
Staff on duty feel like prison warders awaiting a riot. They know that anything could happen. Common sense has disappeared. Children arrive in school wet, wanting to go home to get dry clothes and then get those wet on their return.
Attendance is down. A day in school is not sufficient compensation for getting wet. Better to bond with your duvet. And who can blame them?
Your classroom will be damp and enclosed. There might be water dripping through light fittings from the floor above. Wet, unhappy children will bring their own pervading aroma to your lesson.
If the water hasn't already forced its way through the windows, you can be sure some prat will open one to shout some form of abuse at his cousin and soak a set of textbooks.
You will look at your dysfunctional building and then laugh in the face of the idea of "20th-century schools".
Window sills will be awash with water, inadequately mopped up with old newspapers. No one should have to work like this in our modern world - but sadly you do.
The floors are wet and slippery, bringing an instability which matches perfectly the class that stares back at you. Their bags are soaking, their exercise books wet and limp, their worksheets disintegrating.
The rain has an air of mystery. It falls from the sky unexpectedly and for no reason. No one seems to know quite what to do. It always seems to catch children by surprise. Such surprise in fact that they can't bring a coat.
Parents will drive their children as close to the door as possible, oblivious to even the most basic rules of the road. You might think a coat would be more effective.
Perhaps one day fashion will change. It will dictate that all children should come to school wearing a coat, no matter what the weather. Without a coat, you will be bullied and ridiculed. Today, we dress all year for summer, a season which largely passes us by in an instant.
Rain is not our only enemy. All teachers know that when the wind blows on children, it seems to enter their souls. They are excitable, a little mad. They become loud, physical, slightly hysterical.
There is the look of misrule in their eyes. They seem to be blown around the school without control, like litter, their eyes wide with a lust for disruption and argument.
Yet here can be no pleasure when the grey mist seeps in and wraps you in its monochrome world. Dull world, dull lessons. You want to go home and close the curtains and seek out the sun on daytime television.
But the summer isn't the answer either. There are those very rare occasions when it is too hot to work, or so you will be told. Half the class can't work because the sun is in their eyes and the other half have hayfever.
After a hot weekend, Year 9 are sun-drunk, their flesh peeling. The school will resound to screams as their third-degree burns are slapped for fun.
We can't influence the weather and you can't always influence the pupils. Generally, they behave because there is a tacit understanding that they will. But when the weather takes a hold, that agreement goes out of the window. Oh yes, we are at the mercy of the climate, and you can be sure it is vindictive.
Geoff Brookes is deputy head of Cefn Hengoed School in Swansea.