I waited until the last person had left the classroom. Mrs Cuffy and I were alone. She plonked herself into her chair and took out a magazine. I shot my hand into the air.

‘Miss?’ I said. ‘Please can I come to the front and collect my homework?’

‘Too dim to do it from memory, are we?’ said Mrs Cuffy. ‘Very well. But don’t disturb me again – and don’t speak to that little friend of yours when she comes back. I hope Mrs Winkle gives her what for!’

I pressed my lips together, slipped a pencil into my pocket and crept towards Mrs Cuffy’s desk. I took my fishy-smelling homework from the pile – and dropped it on the floor on purpose.

‘Clumsy clot!’ said Mrs Cuffy. Her beady little eyes stared at me for a second and then she went back to reading her magazine.

I dropped down onto my knees to make her think I was picking up my homework – but really I was quickly drawing a small five-pointed magic star on the floor with my pencil!

When I’d finished, I stood up and stepped inside the star. I put my hands on my hips, took a deep breath and waited. Mrs Cuffy glanced up at me and glared. Her moustache twitched with irritation.

‘Anna Kelly!’ she shouted. ‘What do you think you’re doing, standing there like an idiot? Get back to your seat at once!’

‘I will go back to my seat, Mrs Cuffy,’ I said. ‘But not until you promise to let Mary go to gym instead of detention, and say sorry for making her cry!’

‘Say sorry!’ spluttered Mrs Cuffy, dropping her magazine in shock. ‘Apologise to a pupil? Me? Are you mad?’

I squared my shoulders.

‘What you did wasn’t fair, Mrs Cuffy,’ I said. ‘And I’m giving you one last chance to make amends!’

‘You are giving me a chance?’ said Mrs Cuffy slowly, as if she couldn’t believe her ears. Then she leapt out of her chair.

‘How dare you!’ she shouted. ‘I’ve never been spoken to like that in my life!’ She picked up a ruler and advanced towards me.

I caught my breath. Surely she wasn’t going to clobber me!

‘It’s about time you got what we used to call six of the best, my girl!’ she said. ‘Six of the best wallops I can give you!’

That was going too far. Detention is one thing but even I know that hitting is wrong. It was time for Plan B.

I planted my two feet firmly in the magic star, pointed my finger at Mrs Cuffy and said the first rhyme that came into my head.

Straight away I felt the power of magic surging from the floor beneath me. It shot through my legs, into my whole body, and out through the finger that pointed at Mrs Cuffy. A blue flash of light blinded me.

When the smoke cleared, sitting on the chair where Mrs Cuffy had been, was a large, greasy brown RAT!