A long answer. Let us assume that schools are following a code emphasis approach to reading instruction and not a meaning emphasis model (whole language). This approach requires letter-sound correspondences to be taught in sequence to build mastery of the alphabetic principle...
It also assumes that pupils practice with controlled texts to build fluent decoding skills. Controlled text is written to maximise the use of words with the taught phonic patterns (Rayner et al. 2012) - decodable texts in other words.
Pupils initially work harder to decode texts word by word than to read text composed of memorised words. The letter by letter processing involved builds the high quality lexical representations needed to support quick and accurate reading (Perfetti, 1992).
Chall's (1967) review of reading studies revealed that the time spent reading learned letter-sound patterns was key to progress in reading enabling children to practice decoding in an environment that they would be successful rather than frustrated.
Controlled texts provide children with practice sounding out words on an ad hoc basis while reading sentences. As the quality of lexical representations improves words become more familiar and are read more quickly. The result is reading fluency (Rayner, 2002).
But the question was: should children decodable texts exclusively? What happens if they don't? They will encounter words that they do not have the phonic knowledge to decode. What happens then.
Less skilled early readers compensate for slower or poorer word identification by relying more on context cues to facilitate word identification (Stanovich et al., 1981). In other words...they guess the word. A very inefficient method of word recognition (Ehrlich,1981).
So,it would appear that by encouraging early readers to practice decoding(which is what they are doing; they are not practicing reading)using texts that have not been controlled for taught phonic knowledge, we are encouraging them to identify words in the manner of poor readers.
It would seem that the sole use of decodable text for early decoding is thus essential. It certainly lacks the romance associated with 'whole language'and a love of reading but the best way to ensure children hate reading is to ensure that they cannot read the words on the page.
Code emphasis classrooms, because of the labour intensive nature of early decoding, must also include time listening to children's literature and extensive exposure to a language rich environment (Rayner et al., 2012).
