Physical Activity Before, During, and After the School Day and Its Impact on Positive Psychological Variables: A Systematic Review and Practical Guide

Background/Objectives: Positive psychological constructs such as psychological well-being, resilience, subjective vitality, and mental toughness are fundamental to students’ emotional adjustment and overall development. Physical activity (PA) is a modifiable factor known to enhance these variables; however, the influence of its timing throughout the day remains underexplored. This systematic review aimed to examine the effects of PA on psychological well-being, resilience, subjective vitality, and mental toughness in children and adolescents, considering the timing of implementation—before, during, or after school hours—and the specific characteristics of the activities performed. Methods: Following the PRISMA guidelines, a comprehensive search was conducted in Scopus, PubMed, ERIC, and Web of Science, identifying 29 studies published between 2014 and 2026, comprising 12 cross-sectional and 17 longitudinal studies. Results: Overall, PA was positively associated with all four psychological variables across different times of the day. PA before school, such as active commuting and active starts, was primarily associated with higher in well-being and vitality. During-school interventions, particularly structured programs such as active breaks and cooperative games, were associated with better resilience, emotional self-regulation, and prosocial behavior. After-school PA, especially organized and voluntary activities, was associated with higher resilience and mental toughness. The effects varied according to the intensity, structure, social context, and student role, with moderate-to-vigorous intensities and cooperative formats producing the most consistent benefits. Conclusions: In conclusion, PA appears to exert a beneficial influence on positive psychological development, with variations depending on the time and mode of practice. Schools, particularly through Physical Education programs, constitute a key context for promoting students’ emotional, motivational, and behavioral health.