This sound is /s/, as in the word 'sigh.' The International Phonetic Alphabet (IPA) represents this phoneme with the following symbol: s. In the early stages of the curriculum, Once’s instructional content represents the sound with a symbol that is made by typing ‘s’ in a specialized font. This specialized orthography helps beginning readers (pre-kindergarten students through early elementary grades) learn letter-sound correspondence more quickly. By the middle stages of the curriculum, the specialized orthography is phased out and replaced by letters in a serif font.
