Jemima Lewis: Be your own English tutor – keep a diary

When it comes to language, there is no better teacher than your own mistakes

The Reverend Robert Shields might seem an unlikely role model for British schoolchildren, but – as they say in call centres – bear with me. Shields, a former pastor from Washington state, who died last week at the age of 89, was a little on the eccentric side. For a quarter of a century, he devoted his life to writing his diary – every five minutes. He documented everything, from his bowel movements to the precise contents of his junk mail. At night, he would wake every two hours in order to record his dreams.

Shields was assisted in this time-consuming task by the skills he learnt from his father – the 1904 World Speed Typing champion. He had six typewriters ranged around the house, at which he could clatter off such immortal entries as "7.35-7.40. I peed again and took a methylpredisone tablet" or "9.35-9.40. I cleaned the cerumen from both my ears and from both my hearing aids".

Nevertheless, his hobby did take its toll on his private life. Interviewed once on National Public Radio, he admitted that he seldom left the house. "I don't like to be away overnight, because it gets me behind. If I travel to [the local town] to do shopping, it puts me behind in the diary. I have to take notes all the time, and I get back and it takes me a day to catch up with the notes. So I avoid going out." Asked what his wife and family thought about all this, he replied: "I never asked them," as if surprised to be reminded of their existence.

Shields claimed to be toiling on behalf of future historians, for whom a 37.5 million-word chronicle of a – relatively – ordinary American life might prove invaluable. (To that end, he also stuck in one of his nostril hairs, so that future scientists could study his DNA.) But clearly, Shields was driven by more than mere philanthropy. He was, as any habitual diary-writer will recognise, in the jaws of an addiction.

As the Government surveys the ruins of its £500m National Literacy Strategy – derided this week by Cambridge University researchers for making a "barely noticeable" impression on standards – Shields's obsession may provide a clue to a better way.

The problem with the current strategy, says the report, is that it puts too much emphasis on examining pupils, and not enough on the pleasures of the written word. Primary school teachers feel under intense pressure to deliver high test scores, which they do by coaching pupils within a narrow curriculum, and by giving endless practice multiple-choice tests – as if learning English were much the same as swotting for a driving theory test.

It is hardly surprising that children are bored by this Gradgrindian approach to language. If you want children to love words for their own sake, you first have to teach them to love their own words. And nothing does that better than a diary.

I started writing a diary when I was 12, under orders from my English teacher. "It will teach you discipline, broaden your vocabulary and make you think about how sentences work," she declared. To my amazement, she was right on every count. Congenitally lazy in most respects, I was soon spending every night hunched at my desk, chewing my tongue with concentration as I documented the daily minutiae of childhood.

As adolescence set in, with its attendant dramas, the writing became increasingly urgent and prolix. I would carry my diary with me at all times, dashing into the school lavatories to record the latest "scandal" in terms of the utmost hyperbole. Like Rev Shields, I was more interested in posterity than privacy: I fantasised about literary biographers, a hundred years hence, rocking with laughter at my ironical description of Susan and Trevor's first snog. Sometimes I would get so carried away by my accomplishments that I would pencil an admiring comment of my own in the margin ("Ha, ha! Witty!").

Which brings me to the real point. When it comes to language, there is no better teacher than your own mistakes. I cannot remember the exact moment I first became embarrassed while re-reading my diary – the moment when the verbal fireworks and feigned worldliness began to appal rather than delight – but I do remember, over the years that followed, consciously tweaking my style again and again in the hopes of earning back my own good opinion.

Gradually, I learned to tone it down: to prune back the superlatives and the adjectives, to rely more – like Rev Shields – on the facts to tell the story. And because I was able to learn all this in private (unlike a blogger, whose faltering literary progress may be recorded in hyperspace for the rest of time), the humiliation was at least contained.

These days, I cannot read any of my old diaries: the shame still makes my armpits prickle and my palms sweat. They are locked in a suitcase in the attic, a testimony to the hubris of youth.

Literary biographers will have no use for them, but I cannot throw them away. They were my cruellest, least forgiving tutors – and the ones that taught me most.