Those that can, do: those that can’t, teach. Isn’t that how it goes? Haven’t we all heard that one before at some point in our careers? Or is it only me, and is the teacher’s paranoia starting to get to me already? It was certainly the message I heard loud and clear throughout my PhD.

I’d start at the beginning, except there really isn’t a beginning with teaching. It’s one of those things that has always been there without my really noticing, like background music. But to give you a starting point, “here” is a truly comprehensive school, and I’m a science NQT. I’m slightly different from some as I’m older - 37, in case you were wondering - and have responsibilities.

Not the sort of responsibilities you get paid any extra for, just the sort that mean you have to do other things sometimes than simply worry about your teaching. Like your own children.

And I’m not old. I’m “mature” and, as such, I am an asset to the teaching profession as I bring to it Other Life Experiences.

I went to ordinary primary and secondary schools, in what I now know to classify as “inner city”. In primary, I helped in the office with dinner money and made tea for the staff, and in secondary I did an extra O-level in my games lessons.

My careers advice consisted of asking what your parents did (bus driver and pottery worker), and confirming that that would be your path, too. And in those days of high employment, probably it was. I left school at 15, became pregnant at 16 and promptly dropped out of college and the educational system for years. I got married, brought up my child - and variously one or two of my husband’s - worked in his shop, cleaned for England and kept a good table. I didn’t think for years. Occasionally I did some adult literacy teaching, usually with ex-miners who’d been driven to seek help as they couldn’t read to their children or write notes to school or, as the economic situation worsened, fill in job application forms.

You’re ahead of me. You know that something happened. My husband died. I was 25, I had a nine-year-old son and an 18-year-old stepson, and no apparent means of support. Nine O-levels, then a large gap. I found work in sales and cleaning as I wasn’t qualified for much else. It was time for a rethink. Clearly, I needed some bits of paper to show that I had a brain, or I couldn’t earn a decent living. I found my way to university. Keele was very tolerant of mature students and overlooked details such as A-levels - or the lack of them. Those were also the days of grants. So there I was, by the skin of my teeth, front and centre, earnestness personified. I was painfully anxious, knowing I wouldn’t get another chance.

Personally, it proved to be the perfect answer to my situation as I could get my head around the chemistry far more easily than what was going on in my personal life. Teaching continued, though inadvertently. I became ill, and my case was unusual enough to be used as a teaching aid for doctors. I got better, married again, had another child, and was asked to stay on for my doctorate. I felt as if I had only got half way through the story with my chemistry, and didn’t know what the ending was, so I did stay on.

I became ill again (different condition this time). Pictures of different parts of my body were used as a teaching aid for doctors. I taught undergraduates practical work. I worked in Sicily for a while. I tutored privately and variously throughout all this. Most notably, I tutored dyslexic undergraduate science students, but also maths and chemistry. I taught confidence and self-belief rather than a subject, because that was what they (and I) had been missing. After I wrote up, I took time out and worked as a yard girl at the local stables. Then all my students finished whatever it was they were doing, and they did well. Hey, I thought, perhaps there’s something in this. Perhaps I’d better learn how to do it properly.

Well, I haven’t quite learned that yet, but that took me to my PGCE. I went back to Keele, feeling rather embarrassed at being an eternal student. There I was, afflicted by the same curse of mature student intensity. Some people on the course were straight from their degrees, with the ultimate ambition of going to teach at their old schools, which seemed to be a bit like the educational equivalent of the Oedipus complex. The first few lectures left me with a sense of outrage at all the seemingly ill-considered changes education had suffered since I had last looked. I had a sense that schools were now very different places from those I had known, but confidence was still high. I then went into primary school, and that’s where the shocks began.

The staff were friendly and welcoming, and all worked incredibly hard. But I found a beleaguered profession, doing their very best to cope at the sharp end of government initiatives. The pupils were much as I had expected, having a youngster of my own, although I hadn’t expected the reaction I got from some Year 5 boys when I took off my jacket. They collapsed into huddled sniggers every time I went near them, until I cottoned on and put my jacket back on again. But the biggest shock was what was happening with special needs pupils. All classes had them, of course, to one extent or another. But I had come in fresh from tutoring them at university, where although money wasn’t exactly freely available, it was there for support. This was not the case in primary school, and although the staff did everything they could, the situation was far from ideal. I wondered how my students had ever got where they did. Why wasn’t there more money at the bottom end?

Secondary practice was the next big shock. Walking down the corridors for the first time, I expected the multitudes to part like the Red Sea at my approach. Wrong. I spent the first two weeks surreptitiously scanning teachers’ faces to try to work out if this sort of thing was the norm. It was. I was welcomed with a grunt of “PhD. Huh. You’ll know a lot about very little, then. Bet your physics is weak. We’ll give you plenty of that.”

The ambient temperature continued to drop and I took to wandering the school throughout lunchtimes, finding the pupils more congenial company. It came as no surprise that my first, much anticipated, lesson was physics, Year 10. I wouldn’t say that it was an unqualified disaster. Not quite. I clutched my reams of lesson plan and knew what I was going to say off by heart. Unfortunately, the pupils hadn’t read the same script, and gave answers that were not on my crib sheet. I rallied bravely: “That’s a very interesting point...”, but the real problem was pace. I had been used to teaching one-to-one, as slow as you like, and this approach did not transfer well to whole-class teaching. Another re-adjustment required.

At the same time, work back at base was still going on, and I learned more about my personal inadequacies. I hadn’t properly realised the gulf between learning and understanding. I had been very good at learning, and the understanding had come much, much later. So I had to go back and learn to understand and to put over ideas and concepts that I had always accepted at face value.

I also learned I was primarily a textual-based learner, and many of my pupils were not. Overall, it was like discovering a whole new subject, but I still didn’t learn how to cope with Year 10 after lunch on a wet day.

The second practice was better. I was given classes that were potentially teachable, who patiently tolerated my rather wobbly new techniques. But alongside this came the lemming-like drive to get a job, and the joys of the interview process. I don’t know of any other profession that has anything like it. “You are the Weakest Link. Let’s debrief. How do you think the interviewsactivities went?” (Well, hazarding a guess, being as we’re having this conversation, “not well” seems a reasonable guess.) By interview three, I was beginning to get the message that being happy enough in front of the kids seemed to count for less than my performance in front of an interview panel. Luckily, my present school had a lot of things going for it. They wanted a chemist, they overlooked my stunningly mediocre performance at interview, the staff seemed friendly and they had no other candidates.

This fulfilled my criteria of a) needing to start somewhere and b) in the light of my first practice, friendly staff were an added incentive. I then spent the whole of the summer fretting, trying to literally put my house in order and generally to “be prepared”. I wasn’t. For the first two minutes, I savoured the giddy joy of shutting the classroom door and not being watched. It didn’t last. It dawned that I was on my own, with no one to come to the rescue when things got sticky.

And they very quickly did. Children don’t really like change. They were not at all pleased to see me and my let’s-make-a-firm-but-positive start. By lesson two, one of them ran off. I managed to make it to the end of the lesson and into the prep room before I cried.

The staff have been very supportive, and I have learned how to ask for help, but sometimes I haven’t known what questions to ask. My learning curve has been very steep, and is still rising rapidly. Perhaps it’s just the “November blues”, but I am exhausted, demoralised, working harder than ever and never quite getting on top of things.

I can’t sleep properly and feel inadequate. I take home piles of work that I am too tired to do, and it ruins my evening. Going into the staffroom still terrifies me. At the same time, I am elated when “the light goes on”, excited, convinced that the next lesson is going to be better and I have found unknown reserves within myself.

Teaching has taken over my life - contrary to my avowed intention at the outset. I have lost touch with friends, my family are neglected and my house is a health hazard. It’s the best and the worst thing I have ever done.

I am determined to hold on to my ideals that children respond better to a carrot than a stick and that I can and do make a difference. But I have had to lower my standards, and accept that I can’t always make a difference to everyone, not all the time. Sometimes I think the biggest difference has been made to me, as I’m learning much more than I’ve taught. I have sat on many sides of the fence - pupil, parent, student, teacher, and this side seems to be the best. I pretend to myself I could walk away and find an easier way of earning a living, but I suspect it’s too late. I’m hooked.

Dr Kristina Humphries is a chemistry NQT at Kind Edward VI High School in Stafford