I’d been working as a marketing and advertising copywriter for nearly four years, and as the silver-tongued voice-over explained how the latest combination of vitamin compounds, amino proteins and extract of Something Vaguely Exotic could make my hair 67 per cent more sleek ‘n’ shiny, I found myself asking two fundamental questions. How do you measure sleek ‘n’ shininess? Is there a before and after test on a sleek ‘n’ shiny-o-meter? And do I want to do this anymore?

Teaching was always the career I wished I wanted to do. My father is a teacher and has always loved it. As an English graduate, I know a lot of people who’ve gone into the profession, and few have regretted it. And even though no one mentions it on their PGCE application, six weeks off in the summer is an appealing prospect.

Even so, teaching was not for me. I wanted to work in the real world. I wanted the cut and thrust of a challenging, adult environment. I wanted to go places and be somebody. I wanted to work on projects and be kept in the loop.

But after a few years, I started to wonder whether advertising and teaching were really so different. You have to work out what makes an audience tick and use that to sell them something they didn’t realise they wanted; that can be beer with a widget or it can be double maths. In fact, the only real difference I could find was that with teaching the feedback on how successful you are is instantaneous; market research can be wished away, sales figures can be doctored, but a room full of bored adolescents is harder to ignore.

The more I thought about it, the more attractive teaching became. I organised a few observation days at some local schools and was hooked by lunchtime on my first day. I struggle not to lapse into cliche when explaining to people why I want to become a teacher, but ironically my main reason is a desire to face the challenges I hoped to find in my first career, but never did. Namely, discovering new and creative ways of making a subject appeal to a potentially sceptical audience; having to understand how a particular group of people think, in order to pitch a message at the right level. Except this time I will actually care about that message and believe it to be worthwhile. I don’t, therefore, see my changing careers as trying something new, but rather using the skills I possess with a genuine purpose in mind.

I have a place on a GTP scheme that starts in September and I can’t wait.

Meanwhile, of course, I remain in the marketing and advertising fold. My employers know of my decision and are very supportive. I continue to work hard, but I know my heart is no longer in it. I have found that once you begin to question what you do, it’s hard to stop. Isn’t this just soap for hair? How much closer can a shave get without taking off a layer of skin?

I am not so naive as to assume teaching is one long walk in the rose garden. I know it will be demanding and that there will be countless knocks to my idealism, but surely it can’t be as dispiriting as meeting a communications director who “doesn’t believe in the internet”? Or spending six months working on a brochure before the client realises they forgot to tell you about one of the products. Besides, if nothing else, it will be nice to have some idealism to knock. Why do I want to be a teacher? Because I’m worth it.

Jamie Kirkaldy Jamie Kirkaldy is an advertising copywriter. His GTP is at a secondary school in Hampshire