Her head is like a sieve. Information given to her is never going to be retained. In short, she is un-teachable.” This cheerful analysis was given to my parents at various stages in my education. I couldn’t read until I was 14. Now, having had my own three children, I realise the alarm that this must have caused my parents during my schooldays in the late Fifties and Sixties.

The trouble is, where do you send a child who doesn’t fit into the education system, and who appears similar to her peers in every other respect? I spent my primary years in a selection of small independent schools in London, with patches of home tuition. My main memory of primary school is being told to keep quiet and being left with Janet and John books. When I sat my 11-plus in 1964, I drew frogs all over the exam paper.

I was asked to leave that school soon after, just as I had been asked to leave the one before. In desperation, my parents took me to see a terrifying woman in Sloane Square who gave me a set of tasks, which I couldn’t do. She pronounced that I was “word blind”, and it seemed to me that she was right.

Words simply didn’t stay on the page; they floated past. They were intangible riddles, beautiful in themselves, and I was overawed by them.

Once I was diagnosed as having dyslexia, I was able to return to school - I had missed a year and it was made clear that not much could be expected of me in the way of exams or higher education. With hopeful optimism that, at last, I might muddle through, I was sent to another small private school in South Kensington, said to be forward-thinking. After six weeks I was expelled for hitting a girl. At the time I didn’t have the confidence to say boo to a wombat, let alone the courage needed to bash anybody. Finally, the awful truth came out, far more awful than the idea of my being a violent bully. The headmistress confessed that she didn’t know what to make of me and thought my disability was far too serious for the institution to cope with. By this point I was a teenager who couldn’t even spell her own name; I had been christened Sarah, but I had trouble remembering where the “h” went.

After another term with nowhere to go, I was sent to Horncastle in Sussex, a state boarding school for what were then called maladjusted children.

When I arrived almost the first thing I was told by a fellow pupil was that no one was there unless they had done something really bad. Dyslexia seemed almost a cruel joke compared to what my new companions had been through.

Most of them had seen more than the turnstile to hell, and had serious emotional and behavioural difficulties. Teaching wasn’t high on the school agenda: if I wished to draw frogs, I could draw frogs. Somehow, once the pressure was off, I was able to absorb what I had been taught over the years. One wet Saturday I found the complete works of the Bront s and started to read Wuthering Heights. Without realising it, I had found the small door that had eluded me for so long in the glass wall; there it was, this land of books. I read the Bront s from cover to cover. I found it hard, but I got better with practice.

I went on to sit my O-levels at a “smart” girls’ boarding school. I hated it with a passion, missed the camaraderie of Horncastle and couldn’t wait to leave. My mother promised that if I got an O-level she would see about getting me into art school. I got five O-levels, did an art A-level at a small art school in Hampstead and received a first class honours degree in theatre design at Central Art School (now Central St Martins).

I would like to say that I had mastered my dyslexia by this point. Far from it. Throughout my career in the theatre, dyslexia continued to haunt me. It was like a tin can hanging round my neck, tripping me up or clattering every time I turned a corner; there was no escaping it. In the 1980s, after my children were born, I started illustrating books. Feeling older and wiser, I told everyone in publishing that I was dyslexic. And here, in the world of words, a small miracle happened.

I met Judith Elliott, my editor at Orion Children’s Books, who saw no problem. I had imagination and ideas by the bucketful: what I lacked was confidence. With her gentle guidance I began to think the impossible, that I might write. I had always told myself stories; when you don’t read till quite late in life, you need something to keep you going. I could lose time with my tales, travel out of classrooms, explore new cities, new worlds. I had a cinema in my head, its pictures always perfect. It was my ability to tell ghost stories that had put an end to bullying at my last school. When my marriage broke down, illustrating was not enough to keep the wolf from the door, so I started to write and slowly began to realise that by a roundabout route I had finally found what I loved doing best.

I still can’t spell. I am still dyslexic. I always will be. I now see my dyslexia as a gift. It has given me more than it has taken away. The trouble with dyslexia is that other people around us foolishly believe they have the upper hand. My great fear is that one day the gene that causes dyslexia will be found. I am sure then that parents and educators will hanker for it to be eradicated. But at what cost? We still have a lot to learn about dyslexia. I believe it could be the key to creativity. Maybe the answer lies in thinking in a more imaginative and far-reaching way of how to teach the allegedly un-teachable.

Sally Gardner’s first longer novel for children, I, Coriander, is published by Orion Children’s Books and is reviewed on page 26. The primary national strategy’s 2005 document, Teaching and Learning for Dyslexic Children, is available at www.standards.dfes.gov.ukprimarypublications. Other research updates and resources at www.teachernet.gov.uk