How decodable should a decodable book be?

At the earliest stages, writing a story worth reading using only the spellings a child has learned is extremely restrictive. Most series therefore allow a few common words the child will need help with.

So, the useful question is not whether every word is decodable. It is which words are not, how many, and whether the book tells you. Surprisingly often it does not.

Book one of Tip Top Phonics has five spellings: s, a, t, i, m. Its reading list is five words.

Mim · Sam · sit · mat · Tam

Two people, a mammoth, an object and a verb. Add a and is and you can write a sentence: It is Sam. Tam is at a mat. Sit, Tam!

Helper words and story words

Not all undeclared words cause the same trouble. This is not universal phonics terminology. It is the distinction we use when editing Tip Top Phonics, and it does more work than the usual categories.

Helper words are function words. A child meets them a thousand times in the first year and they carry almost no meaning alone. Naming a few and telling the parent to supply them is sensible practice.

Story words carry the story. A book about a fox that uses fox before x is taught puts the child in an impossible position: they need the word to follow the plot, they will be asked to read it, and they cannot.

Story words are often the payoff of a later book, too. If x is book seven's job, spending fox in book four teaches the child to recognise a word they should be learning to decode.

A worked example: why ‘is’ is a helper word

Is looks decodable. A child who knows s, a, t, i and m can see two familiar letters, and a parent would reasonably expect them to sound it out.

They cannot. The s in is spells /z/. Sounding it out with the correspondence they have been taught gives "iss".

So is is named as a helper word on book one's front matter, alongside a. It appears in almost every book of Set 1 and it is flagged every time.

There is another way to handle this. Some programmes, particularly those working from sound to spelling, teach s spelling /z/ as a correspondence in its own right, so is, has and his become decodable instead of declared. Both routes work. What does not work is doing neither and leaving the word in a first book as though it were as regular as sit.

How the list should grow

Set 1 declares its helper words book by book.

Seven words across a whole set. That restraint is the point.

Percentages

You will see decodability quoted as a figure: ninety per cent, ninety-five, one hundred. Treat these carefully, because they can be calculated several ways and the method is rarely stated.

Running words counts every word on the page. The thirty times counts thirty times, which inflates the figure, because helper words repeat more than anything else.

Unique words counts each different word once. Lower, and usually more honest.

A book can be ninety-eight per cent decodable by running words and still have four words on a spread that stop your child dead. And no percentage tells you whether the book matches what your child has been taught, which is the only question that decides the evening.

Read a page. It tells you more than a figure on a back cover.

Where we draw the line

Helper words are named and few. Every book lists its own. We add them slowly.

Story words wait. Fox waits for book seven of Set 1. Thud the sabre-toothed cat has no name at all until book six of Set 2, because his name needs th. ck waits until book seven of Set 2.

Pictures never carry a word. If the only route to a word is the illustration, the sentence gets rewritten.

No word appears that cannot be reached by sounding out. Not by pattern, not by rhyme, not by repeated sentence frames.

Reasonable publishers draw these lines in slightly different places. Be wary of the ones who have not drawn one at all.

Sources

Department for Education (2023) The Reading Framework. gov.uk