Articulation of speech sounds follows a typical developmental pattern, reflected in standard age norms. Mostly intelligible speech should be heard by 3 years of age. Children with speech sound disorder continue to use immature phonological simplification processes past the age most children can pronounce words clearly.

The most frequently mispronounced sounds in English also tend to be learned later, (l, r, s, z, th, ch, dzh, and zh). Misarticulation of any of these sounds by itself could be considered within normal limits up to age 8 years of age; however, when multiple sounds are involved, it is important to target some of those sounds as part of a plan to improve intelligibility.

Most children with speech sound disorder respond well to treatment and the disorder may not be lifelong. However when a language disorder's present prognosis is poorer it may be associated with a learning disorder.