Search for: [Abstract = The article discusses the specific character of changes in the assessment of the sense of social integration in the classroom between primary school third\- and sixth\-graders, and their social, demographic and cognitive determinants, with special consideration given to a pupil’s position in the sociometric network. The analysis of latent growth curves – based on a scalar longitudinal measurement invariance, the bifactor model of the Perceived Peer Integration Questionnaire \(PPI\) and three rounds of the nationwide study School determinants of educational effectiveness \(N = 4349\) – indicates that the second stage of learning in primary school is characterised by a more negative perception of peer integration in classroom settings, which cannot be explained by socio\-demographic variables nor the relationships taking place within peer networks. This indicates that it may be linked to developmental changes rather than to the actual deterioration of peer relations.]