Self-concept can be defined as a structured, multidimensional, and evolving construct that constitutes all the beliefs that an individual has about him/herself. Among its dimensions is the physical dimension that encompasses perceptions of physical attractiveness, self-esteem, and physical condition. The purpose of this cross-sectional study was to look for differences between the educational stages from the third cycle of primary school and high school, as well as to study the possible correlations between the age groups and the dimensions of the scale. The AF-5 scale was used to measure self-concept, the Kolmogoronov–Smirnov test was applied to determine the normality of the data, Kruskall–Wallis to identify the differences between the dimensions of the scale and the educational stages, and Spearman’s Rho for correlations between dimensions and age groups. Significant differences were found in the academic, emotional, family, and physical dimensions between educational stages and between the scale as a single construct. Significant inverse correlations were also found between age groups and dimensions. Overall self-concept decreases with age and varies according to the educational stage.