Students with speech-language impairment require significant educational adjustments as a result of having a severe ongoing primary spoken communication disorder.
Students with speech-language impairment, like all students, vary in abilities and needs. They will all, however, experience significant difficulties in at least one of the following areas:
(Reference: http://education.qld.gov.au/studentservices/learning/disability/generalinfo/speech-language/sli2.html )
To learn more about how speech and language develop, and typical speech-language developmental milestones, read this article.