The objective of this research was to analyze and elucidate the sagittal spinal posture status in older elementary school children, considering their gender and grade differences. The study involved 484 school children (252 males and 232 females) from grades V to VIII, assessed for sagittal spinal posture using the Formetric 4D System. The analysis, employing the Chi-squared test of independence along with the Z-test, did not reveal significant grade-related differences (p < 0.52) in the incidence of normal sagittal alignment or diagnosed outliers. However, within grade levels, no significant difference was observed for male participants (p < 0.80), while a significant difference was identified for females (p < 0.01). Examining gender differences across grades, a disparity was noted only among seventh graders concerning normal spine alignment and outlier existence (p < 0.01), favoring male participants. Regardless of the grade, a significant gender difference emerged in the location of diagnosed outliers: kyphosis (M = 108 vs. F = 72), lordosis (M = 5 vs. F = 14), kypholordosis (M = 18 vs. F = 66), and flatback outlier of the lumbar spine (M = 27 vs. F = 11). These findings suggest potential adjustments to the curriculum and highlight the need to tailor physical education instruction based on this study's outcomes. Consequently, these results imply the importance of a differentiated approach in preventing sagittal plane outliers of the spine in adolescent children.