Syntactic development allows children to connect different words into sentences and statements which express their desires, interests and opinions. The adoption of new syntactic structures characterizes early syntactic development, and later syntactic development is manifested in the combination of existing structures into longer, complex sentences. A child between the age of three and four is already beginning to form grammatically correct sentences. Syntactic development continues throughout primary school education, slowly, but it is evident that sentences are becoming more complex and meaningfully connected. The purpose of this paper is to determine and compare the basic syntactic features of compositions (self-descriptions) according to the types of sentences produced by two generations of pupils of younger school age, which were written almost two decades apart. In addition to comparing these syntactic features in the compositions of two generations of pupils - past and present, the features within the same generation are also compared considering pupils’ age. To be more specific, self-descriptions in the second and fourth grades will be compared. The comparisons were intended to determine which types of sentences are most used and which are least used by each of these generations in their written expression. The goal is also to discover whether the time interval of almost two decades influenced differences in the production of certain types of sentences. The research included 68 compositions (self-descriptions) in which the participants described themselves. Half of the self-descriptions, 34 of them, were collected in 2001, while the remaining 34 self-descriptions were collected in 2020. The obtained results showed that in both generations simple extended sentences dominate, so complex sentences take up a smaller share than expected. However, certain classes stand out in both generations. In 2001, second-grade pupils used the highest percentage of complex sentences in their self-descriptions, as much as 41.11 %, while in the other participants' groups this percentage was significantly lower. Research has shown that younger school-aged children are still more inclined to write simple extended sentences as well as twenty years ago. Even in the fourth-grade complex sentences are still used less in writing than simple extended ones. During the research, the fourth grade from 2020 stood out because these pupils used the largest number of multiple compound sentences. The fourth graders also showed reduced use of the sentence sequence compared to the second graders and increased production of the compound and opposite sentences, which is certainly an indicator of their syntactic development.