This article concerns internalizing and externalizing behaviors among Polish adolescents attending primary schools in a medium-sized city in Poland. The aim of the study was to examine the levels of select problem behaviors (i.e., depression, withdrawal, somatic complaints, aggressive behaviors, delinquent behaviors, thought problems, and internalizing and externalizing disorders) in early adolescence. Another important aim was to establish the ranges of the norm and deviation which would indicate the need for intervention aimed at internalizing and externalizing disorders in the sample. The relationships between variables such as age, gender, and school achievement (grade average) and the groups of problem behaviors and externalizing and internalizing disorders were also examined. To diagnose the occurrence of internalizing and externalizing behaviors, a sample of 550 students (55.3% girls, 46.7% boys) were measured using the Youth Self-Report (YSR) questionnaire. The results showed statistically significant differences in internalizing and externalizing behaviors between boys and girls. Girls achieved higher scores on most of the YSR scales, including internalizing and externalizing disorders, as well as on the total score. The student subgroup scores were also differentiated in terms of age and their average grades. The results also have practical implications; namely, the need for obligatory screening tests of students' emotional states; encouraging preventive measures in schools, including diagnosis and psychological support in the context of depression; monitoring aggressive behaviors and social problems, both in boys and girls; and implementing universal, selective, and indicated prevention through complex, empirically validated educational-therapeutic programs.
Keywords: Poland; adolescents; externalizing disorders; internalizing disorders.