Explicit instruction in phonics involves systematic and sequential teaching of the letter-sound relationships in written English that allow readers to decode words.
Explicit teaching of phonics is a cornerstone of effective early reading instruction. Around one third of children will have difficulty learning to read without systematic teaching in how to ‘crack the code’ of written English, and another third will not learn to read at all without it.
Phonics instruction is most effective when integrated into a comprehensive literacy program that includes practice with decodable text as well as exposure to literature with a rich vocabulary.
Decades of evidence shows that all children benefit from explicit and early teaching of the correspondences between letters and speech sounds.
There are essentially two approaches to teaching phonics explicitly: synthetic and analytic phonics instruction. Their effectiveness differs markedly. At present the model known as systematic synthetic phonics has the strongest research support.
In synthetic phonics, teachers build up phonic skills from their smallest unit (graphemes). The processes of blending (“What word do these sounds make when we put them together mmm-aaa-nnn?”), and segmenting (“Sound out this word for me”) are also taught.
‘Controlled vocabulary’ stories may be used — books using only words decodable using the students’ current knowledge base. This is intended to reduce the memory load on beginning readers that follows from having too large a range of words at a time when the aim is for students to induce the alphabetic principle.
Analytic phonics involves the analysis (breaking down) of the whole word to its parts. For example, “The sound you want occurs in these words: mad, maple, moon.” Sounds in isolation from words are not presented to children.
In analytic phonics, children learn words by sight at first, and their attention is drawn only to initial letter sounds. Segmenting and blending are introduced after all the letter sounds have been introduced. By contrast, synthetic phonics teaches children to sound and blend from the beginning of reading instruction, after a few letter sounds have been taught.

KEY RESEARCH FINDINGS
RECOMMENDED READING
D’Angiulli, A., Siegel, L.S., & Maggi, S. (2004).
Literacy instruction, SES, and word-reading achievement in English-language learners and children with English as a first language: A longitudinal study.
Learning Disabilities Research & Practice, 19, 202–213.
Dehaene, S. (2009).
Reading in the brain: The science and evolution of a human invention.
Viking/Penguin, New York.
Galuschka, K., Ise, E., Krick, K. & Schulte- Körne, G. (2014).
Effectiveness of treatment approaches for children and adolescents with reading disabilities: A meta-analysis of randomized controlled trials.
PLoS ONE 9(2), p. 9.
Johnston, R., & Watson, J.E. (2005).
The effects of synthetic phonics teaching on reading and spelling attainment: A seven year longitudinal study.
Edinburgh: Scottish Executive Education Department.
Rose, J. (2006).
Independent Review of the Teaching of Early Reading, Final Report.
UK Department for Education and Skills.