The purpose of present study was to explore the perceptions of peers as socialization agents in school adjustment among upper secondary school students. The associations were studied in a sample of 564 Norwegian students. Results showed that perceptions of friends and classmates as socialization agents accounted for unique variances in various measures of school adjustment, when controlled for academic achievement, family financial situation, year of schooling, gender and course of study. The unique effect of peer socialization factors on variances in intentions to quit school, truancy, class absence, school alienation and improved motivation for continued education was 7.9%, 7.2%, 6.8%, 6.5% and 5.3% respectively, indicating that late adolescents' school adjustment is statistically significant, but relatively moderately associated with different aspects of peer socialization. School-obstructive regulation was the variable that accounted for most variances in school adjustment, followed by classmate support and school-supportive regulation. (Contains 4 tables.)