School education is not the only source of acquiring knowledge and skills, recently the role of extracurricular time in developing children's human potential has been increasing (Larson & Verma, 1999; Anickin et al., 2023).

Modern schoolchildren spend a significant part of their time in organized activities. As a rule, activities in clubs and sections are considered a positive factor for children's cognitive and non-cognitive development (Eccles et al., 2003; Mahoney et al., 2006). But among unstructured practices, more productive ones are also identified: hobbies, creativity, reading books, online courses, as well as individual or team sports activities, which contribute to the formation of some skills that contribute to the development of children and adolescents (Dumais, 2006).

In connection with the influence of extracurricular time on the development of children and adolescents, it can be said that time acts as an asset (Larson & Verma, 1999; Syvertsen et al., 2021), which is used to form the child's human potential (Korolenko & Gordievskaya, 2018), which is especially relevant in childhood when the return on productive time investments is highest (Heckman, 2008).

Despite the positive effects of increased organized extracurricular time on child development documented by researchers (Coulangeon, 2018), excessive participation in organized activities (overscheduling) negatively affects overall development, including increased levels of stress and fatigue (Fredricks & Eccles, 2010; Knifsend & Graham, 2012). Therefore, it is extremely important to balance organized and unstructured time to maximize the child's human potential.

Because the effects of extracurricular time on the development of children may be related to the socio-economic and cultural capital of the family (Sirin, 2005), it is worth considering the SES and place of living of the family to determine the contribution of extracurricular time to the development of schoolchildren.

The purpose of this study is to examine and identify the optimal structure of schoolchildren's extracurricular time to maximize the effects on the academic performance and well-being of schoolchildren.

The study uses survey data from 4,029 students in grades 5-11 living in Naro-Fominsk, Moscow region in 2024. A two-stage stratified sampling design was used, with the child's place of living (urban/rural) and grade level as the stratification variables. The student questionnaire contains 75 questions across three main sections: 1) socio-demographic data, including age, gender, grade, family composition, and parental education; 2) extracurricular activities, such as participation in clubs/sports, time spent on tutoring, and time allocation for unstructured practices; and 3) psychological well-being (Opree et al., 2018) and self-reported grades. The data was collected through an online survey completed by students in grades 4-11. The student survey was administered in multiple 30-minute sessions to reduce respondent burden. The dependent variables are academic performance, measured by average grades in math, Russian, and a foreign language, as well as an index of student psychological well-being. Quantitative analysis was conducted using descriptive statistics, correlation, and regression. Regression models were used to test for potential non-linear (U-shaped) relationships between students' organized/unstructured time and academic/well-being outcomes.

The results demonstrate differences in out-of-school time use structures among students with different SES and place of living. The identified relationships between time use also indicate a stronger association between organized time and academic performance as well as student well-being. However, a threshold was found, beyond which organized time no longer shows a significant positive correlation with academic performance and instead reduces student well-being. This suggests an optimal balance between organized and free time, where academic performance and student well-being reach their maximum levels. The findings of this study can be used to organize students' daily routines and leisure time, as well as to develop educational programs and extracurricular activities, taking into account students' needs for free time and the context of their family's SES and residence.

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