Primary schools are by their nature colourful places. A display of paintings inspired by Bach’s “Air on a G String” hangs inside the entrance to Harwich Community Primary School, suffused with greens and yellows. Up the corridor are geometric pictures of tessellations, deep with oranges and purples.

What you tend to see less often in primaries is this riot of colour in children’s written work. But one teacher at the school is convinced that using colour in writing can make a difference to what pupils achieve not just in literacy but across the curriculum, and she’s setting out to prove it.

That’s not colourful writing as in purple prose, by the way. Annette Watson-Morse arrives at lessons armed with a clutch of felt pens and highlighters, often purchased from her own pocket. Her pupils write stories and essays in rainbows and highlight comprehension passages in yellow, green and pink. Even their maths calculations cover the rainbow.

“The boys especially like writing in colours,” she says, “because they can write in the colours of their football team.

“It works as a motivational tool. One child told me it turns writing into art, and I definitely agree. They see themselves as doing something that perhaps they shouldn’t be doing and that’s always an attraction.”

Motivation is important here. Harwich primary was until recently designated with serious weaknesses. Harwich could be described as the end of Essex: go much past the school and you fall into the North Sea. The attractive surroundings mask extensive poverty.

But Annette also believes colour helps younger children recognise words and older pupils learn to structure their writing and grasp concepts such as paragraphs. It has also improved their performance at comprehension.

In Year 6, pupils are putting the finishing touches to essays about an alien school. It doesn’t sound the sort of place where you’d want to teach, what with the Godzilla slug trails left by students and the toenail and bogey school dinners. Someone should tell Ofsted.

What’s almost as striking as the vividness of the prose is the vividness of the writing. Pupils began the exercise with a spider chart, jotting ideas in a web. Each group of related ideas was written in a different colour.

These same colours were then used to sketch paragraphs on different themes - lessons, school buildings and so on. Now the children are putting the whole thing together into a multi-coloured page of prose.

“We have different colours for different subjects, so we can tell them apart and make it a bit more nice,” explains Megan. “The work is really fun. It’s not like normal work.”

Ben says the different colours help in other ways, as well. “Say you’re reading a script and when the father speaks, you colour that green and it’s easier because you know all the green parts are the father.”

The class moves on to a comprehension test. As Annette reads a passage from Tom Sawyer, the children highlight it line by line. After every sentence, she tells them to swap pens - each sentence a different colour. Afterwards, they highlight the questions on their test sheet before setting down the answers.

Annette used this exercise while researching her MA in education. For three weeks, pupils did conventional comprehension tests; then over three weeks they did the same tests again, in colour. The results improved dramatically: pupils scoring more than eight correct answers jumped from 9 per cent to 32 per cent.

Some improvement may be due to maturation, or pupils remembering the questions. “But the improvement was so great, there must be some other reason,” Annette says.

Certainly the pupils see a benefit. Nine out of 10 said they found the coloured sheets easy to understand, compared with six out of 10 for black ink. “If there’s a full stop or punctuation, you might accidentally miss it,” says Kane, 10. “When it’s highlighted it’s easier to read and get information.”

Annette started buying felt-tips after she ran out of Biros at her last school. A former fashion designer, she looked at the array of pens in the stationery shop and thought, why use one colour when you can use six?

She began by getting pupils to write words they were using for the first time in a different colour. But around the same time she attended a training session run by primary literacy guru Sue Palmer, who talked about rainbow colour sentences - using colours to show how different sentences can have different lengths to create an impact. “I was just spellbound,” Annette says. “It just seemed to be the way I think about things.” She began using it in every lesson she teaches.

Headteacher Hilary Allen is supportive. The idea pricked her interest not least because it reminded her of Gettegno’s theories of colour and phonics, in vogue during her own training in the late 1960s (Words in Colour, 1962).

Of course colour has been used in teaching before. Mrs Allen says she taught children at her previous school to use highlighters in note-taking; then there are the coloured overlays used by some special needs teachers to help pupils read, or the multi-sensory approaches of Montessori teaching - or Sue Palmer’s rainbow sentences.

Sue Palmer gives Annette’s work an approving nod: “I think it’s a jolly interesting idea. There’s lots of potential, and she seems to be starting something off.

“She seems to have picked up all sorts of ideas and started exploring them in the classroom. It’s the sort of thing that teachers could apply in their own lessons.”

Annette’s next move is to gather more evidence, indeed, she would like to research it for a PhD. Mrs Allen says that with more data, the technique could become used across the school: “If she can provide data that supports her ideas, I think the staff would be happy to take it on. If it can help some of the children and take the school forward, then more power to her elbow.”