I can’t quite believe that this is my real life. In January, I gave up my teaching job, all but half a day a week. Now I’m a freelance writer, and I have to say so on forms and at parties. (It’s very different, I’ve discovered, from saying you are a teacher. People no longer say, “Teaching? Well I don’t suppose you bother with that grammar stuff”; they say, “Poems? Do they rhyme?”) I’ve read about myself in newspapers, and this morning, startlingly, received publicity about myself from the Poetry Society. It is all very unlikely and precarious.

Each morning when I wake up without the alarm, I am haunted by the fear that I must be late for something. I still feel tension in my back every time I hear the words “teacher” and “government initiative” on the radio, and then remember that the insult can no longer hurt me. I can start work in my dressing gown, clutching my coffee, and when I get weary pop out and do the weeding, or some shopping, or go for a swim. But I do so furtively, glancing over my shoulder as if looking for the deputy head in charge of cover. I feel twinges of teacherliness - fear of bells, lesson plans, students in crisis, of marking reaching crisis point in the in-tray - in the way that amputees are said to feel pain in their missing limb.

I don’t know how my colleagues put up with me. Once a week I go into college and teach in the way everyone should be allowed to - only about what I know, only when I’m fully rested and happy - and tell them how ill they all look. I expect them to rise up and mug me. I don’t feel anyone should be allowed to do this simply on the strength of one volume of poems. I expect, every day, to be stopped.

But then “real life” seems to be a flexible concept. When I started in teaching as a 22-year-old, in the merchant-bankerish Eighties, people frequently used to tell me that I didn’t live in the “real world”. They meant that I didn’t deal with money, I didn’t wear a suit, I stood no chance of getting a Christmas bonus, and I didn’t stay in the office until half past nine attempting to impress the boss. But then these were the kind of people who believed in the housing boom, and that turned out not to be so real after all.

Now, in this strange new world I’ve entered, a world inhabited by writers, journalism and publishing, where everyone has a phone and is constantly on it, where no one has to pay for lunch, teaching seems positively gritty with “realness” and worthiness. My tales of the classroom are missionary stories, as exotic as the strange customs of another tribe. “You used a Banda!” shrieks the publicist, in horror. “But how did you answer the phone?” asks the agent. And, over and over again, people say: “You taught in the state sector? Wasn’t that frightening? How did you manage to do that and write?” I enjoy all this. I feel brave, hardened, street credible, vaguely noble, even though I know that if my interlocutors could see the quiet, carpeted corridors of my sixth-form college, and meet my eminently civilised if not entirely adult students, they would be swiftly disillusioned. I don’t correct them; I think they are at least half right. Teachers should be greeted with awe, and teaching is the most real of worlds, because it is where so much of our emotional landscapes and ideas about ourselves are formed. That is why politicians and people you meet at parties always have such firm ideas of what you should be doing in the classroom; they were at school themselves, and they know all about it. I think it is entirely possible, for example, that John Major’s tragic need to belong to the Tory party and evident need to recreate the kind of school that failed him stemmed from his experience at Rutlish Grammar all those years ago.

They are wrong, though, to think that teaching is a very different thing from writing, or to look on the classroom simply as a source of writing material, a seething mass of raw emotion to draw on. It is true that school life has supplied me with any number of metaphors for the world, but, more importantly, most of my skills as a writer were learned through teaching. Filleting and presenting a single poem to a class of 15-year-olds is a far better way of getting to know the bones and structure of the language than turning out a generalised essay at university. Answering questions from such a class is far more likely to raise interesting points and layers of ambiguity than the automatic comprehension of a sophisticated audience. Selecting work for different age groups makes you endlessly aware of the need for clarity, accessibility and concrete images, and fills you with admiration for the poets who achieve it.

Being an English teacher means that you are generally reading Shakespeare, often once a day, mostly aloud, and absorbing the rhythms, nuances and plots with an intimacy experienced by no one else except a few theatre directors. Teachers learn to be performers - there is no point trying to get students to read with meaning if you can’t do it yourself - and readings are an increasingly important part of a poet’s job. Above all, teaching is an extended exercise in imagination and empathy - not just reading a text for yourself, but thinking out how it it is being received by others. There could be no better training for understanding audiences or creating characters.

These qualities, though, are also exactly what makes teaching so peculiarly exhausting. And it is precisely because teaching and writing are so similar that in the end I found I could no longer combine them successfully. I was exhausted and teaching badly, and ours is a profession in which it is particularly difficult to coast. I can’t imagine, though, a life in which I didn’t have contact with the classroom, which is where so much of my “real life” has happened. Perhaps that is why this freelance business seems so unreal - I’m just taking an unusually long summer holiday, or a sabbatical. I’m sure, at some point soon, I’ll be sharpening my pencils, buying a new red pen, and preparing for battle with the photocopier.

Kate Clanchy teaches at a sixth-form college in Essex Slattern (Chatto and Windus Pounds 6.99) is Kate Clanchy’s first collection. She has won the Forward Poetry Prize for best first collection, the Saltire Prize for Scottish first book of the year and the Somerset Maugham Award. She is shortlisted for the Mail on Sunday John Llewellyn Rees Prize, to be announced on June 18