The suit is pretty much straightforward. Battered certainly, but still serviceable as a uniform. It is the tie that is the problem.

Clothes are apparently all about making an impression. I must often give the impression of a bumbling unco-ordinated oaf - and this despite all the effort I put into selecting the right neckwear.

According to my Year 10 class, I select my ties in the dark. What do they know? They are merely children. They do not know how much thought goes into it. They do not understand the judgements I have to make. It is one of the biggest decisions of the day.

What sort of tie am I going to wear? Or rather, what sort of person shall I be today? Is this an advanced form of schizophrenia, my personality determined by cloth?

I have just the thing for that important meeting. Grey, with a discreet motif. Today I am respectable, a man in control, dispensing wisdom. I will shift large sums of money with barely a sigh. I shall spend my day directing destinies, shaping the future with a calm, knowing smile, respected and respectable. Just like my tie.

But wait. Is today a Disney day? Should I choose instead to be defined by wacky characters? Will I be able to think today only in primary colours? Do I need to think in any other way?

My tie will tell you that I am clearly a man of my people: comfortable, relaxed, approachable, with a ready smile, a cheery joke. See just how much our school is one happy family.

It is not a fashion choice, as my Y10 will quickly confirm. It is all about power, politics and identity. It is also about mood.

Our art teacher often sports a tie featuring Munch’s famous screaming face.

You can always tell what sort of day he is expecting. His sensitivities will be shredded. “I am an art teacher. Get me out of here.”

Perhaps I spy a solution to this daily crisis. Subject specialists should identify themselves through appropriate designs. By their ties shall you know them.

Beethoven? Ah yes, you have come for the music appointment. That man with the Hitler tie? He is a history specialist. At least I hope he is. The head of IT has already started. He has one with all manner of gizmos on it.

Though of course some of them could be soup.

Thinking up an appropriate design for the deputy head should keep the staffroom amused for many happy hours. Mr Bean anyone? Perhaps I can try to influence how you think about me through the selection I make. But I can never know what the day will hold or what is expected of me.

Who must I speak to? Which part of my personality must I lay on the line today? Who will shout at me? Who will I shout at? And do I want them to listen to what I have to say or to stare at my tie?

So in the end I aim always for sober. I do feel rather foolish dealing with an aggressive and abusive parent when I am wearing that special tie with elephants on it that my daughters bought for me. I am always worried that it gives the wrong impression.

Obviously this is not something that my female colleagues need to concern themselves with unduly. But I have never been able to work out whether cleavage is helpful or not when Mr Brown comes to call and is banging his head on the office doorframe.

Does cleavage distract or inflame him? And what would happen if I tried it?

No. Sadly the tie must always be understated. I should remain old and boring and enjoy the holidays when my neck runs wild and free. Sometimes, however, a mood can overtake any of us.

You must collect your girl from the station wearing the jolly tie that she bought you. It is what fathers do.

But it isn’t quite the thing to wear when excluding a pupil for spitting at Mrs Jones. It happened. It was Christmas, and his mother could not take her eyes off Santa.

Geoff Brookes is deputy head at Cefn Hengoed comprehensive, Swansea