This paper presents the results of the research of peculiarities of syntactic development, as an element of language structure on the grammatical level of children suffering from developmental dysphasia, after the completed speech pathology treatment of many years. Syntactic level at younger school age was studied by assessing language competence in the accomplishment of communicative sentence with subordinate clause. The research was performed on the samples of children at school age in regular primary schools in Belgrade. The sample comprised 160 respondents who were divided in two groups: target and comparative. The target group consisted of 60 respondents (children suffering from developmental dysphasia after the completed speech pathology treatment of many years), and the comparative group consisted of 100 respondents from regular primary school "Gavrilo Princip" in Zemun. Research results show that grammatical development of children suffering from developmental dysphasia takes place at a considerably slower rate and entails substantially more difficulties in accomplishing predication in subordinate clauses. This paper discusses the consequences which the difficulties in grammatical development can have on school achievement.