We used an epidemiological study to explore the perception of change in several psychosocial dimensions during the COVID-19 quarantine. We focused on emotions, use of social network sites (SNSs), family life, important relationships, body functions, and school life. Using snowball recruitment, N = 1047 Italian children, pre-adolescents, and adolescents (M = 13.74 ± 3.59) were selected to complete ad hoc online questionnaires. A differential semantic inventory plot was prepared to analyze the emotional experience of children, pre-adolescents, and adolescents during quarantine compared to the pre-quarantine period. The Kruskal–Wallis test was run to assess gender and age differences in emotions experienced, habitual SNS use, and the experience of attending classes remotely. A post hoc Wilcoxon test was performed to compare such differences. Results showed that most of the sample (93.1%) attended classes using technological devices and reported missing their classmates very much (59.3%). Adolescents experienced more negative emotions (M = 3.69 ± 1.33) than pre-adolescents (M = 4.64 ± 1.32), who experienced negative emotions more than children (M = 5.11 ± 1.24). Females were more prone to experience negative emotions compared to males. Adolescents were also the most prolific SNS users (78.1%), particularly female adolescents. Overall, these finding highlight the necessity of preserving the emotional state and relational well-being of youth in these developmental phases by considering their school and social lives.