Even though schooldays last a fraction of a lifetime (a sixth if you start school at 4, leave at 18 and live to 84) they leave a whopping great mark. Schoolteachers can colour our lives for ever, in pretty pinks or ghastly greys. They loom so large in the classroom it can be hard to rate them at the time. But thirty years after leaving school, I feel qualified at last to think about what makes a good teacher.

For some strange reason, it’s easier to define a bad one. Mrs Florris, the principal of Tullybun Primary in my book Class Act, was a joy to write: small-minded, ruthless, competitive, snobby, rude, scornful, intolerant and an Olympic battleaxe. Easy peasy.

But good teachers? No offence Roald Dahl, but I find Matilda’s Miss Honey a bit of a wooss. John Keating in Dead Poets’ Society makes me feel square to the power three, and Professor Bhear in Little Woman is crusty and dusty and a little too noble.

From my own schooldays, and conversations with my daughters and their friends, here are some instructions for a flatpack self-assembly super teacher:-

1.Make lots of jokes but only kind ones. Mockery is out and teasing the slippery slope.

2. Love your subject but don’t be a genius especially if it’s maths. Brilliance can stop you understanding why 2+2 is hard for some.

3. Wear moderately interesting footwear, e.g. odd socks are cute, Minion slippers stupid.

4. NO FAVOURITISM. It can ruin the lives of the unfavoured and the favoured, and will lose you megalegabytes of respect.

5. Smell a bit nice. Faint perfume or aftershave is fine, nuclear Chanel or Lynx that tranquilises at 50 metres is not.

6. Listen listen listen.

7. Bad moods are OK but explain them to the class, e.g. ‘My hamster ate my dog. Anyone who talks today will never talk again.’

8. Encourage encourage encourage encourage encourage encourage encourage encourage. And encourage.