Objective To develop a weight management knowledge assessment scale for primary and secondary school students and evaluate its reliability and validity.

Methods Literature review and Delphi expert consultation (2 rounds) were used to form the initial weight management knowledge assessment scale for primary and secondary school students. A total of 2 611 students from the third grade of primary school to the third grade of senior high school were selected through the convenient sampling method from primary and secondary schools in Tianjin city, Jiangsu province, Hebei province, Hubei province, Sichuan province, and Ningxia Hui Autonomous Region to conduct a formal survey of their weight management knowledge in April to May 2025. The critical ratio method, discrete trend method, factor analysis method, and correlation coefficient method were employed to screen the scale items. The Cronbach′s α coefficient and intra-class correlation coefficient (ICC) were adopted to evaluate the reliability of the scale. The validity of the scale was evaluated based on the item-level content validity index (I-CVI), scale-level content validity index (S-CVI), exploratory factor analysis, intrinsic correlation test, average variance extracted (AVE), composite reliability (CR), factor AVE square root, and comparison of correlation coefficients between this factor and other factors.

Results Through exploratory factor analysis, the weight management knowledge assessment scale for primary and secondary school students was determined to include 40 items in 8 dimensions: preventive cognition, lifelong management, monitoring and evaluation, dietary nutrition, reasonable exercise, sleep psychology, scientific weight loss, and family action, which showed a cumulative variance contribution rate of 76.342%. The Cronbach′s α coefficient of the total scale was 0.825, and that of each subscale was within the range of 0.801–0.896. The ICC was 0.833, and the ICC correlation coefficients varied in the range of 0.811–0.882. The I-CVI of the scale items and the S-CVI were 0.851–1.000 and 0.872, respectively. The results of confirmatory factor analysis showed that the correlation coefficients of the eight common factors—prevention cognition, lifelong management, monitoring and evaluation, dietary nutrition, reasonable exercise, sleep psychology, scientific weight loss, and family action—with the scale were 0.804, 0.811, 0.768, 0.702, 0.811, 0.739, 0.714, and 0.775 (all P<0.01), and the model fit well (χ² = 2 681.847, CFI = 0.901, TLI = 0.891, GFI = 0.869, IFI = 0.903, NFI = 0.882, RMSEA = 0.071). The AVE and CR were in the ranges of 0.532–0.721 and 0.735–0.796, respectively. The dimensional correlation tests of the scale all met the standard and were less than the square root of AVE, and the scale had good validity.

Conclusions The weight management knowledge assessment scale for primary and secondary school students encompasses preventive cognition, lifelong management, monitoring and evaluation, dietary nutrition, reasonable exercise, sleep psychology, scientific weight loss, and family action, demonstrating good reliability and validity. It can be used to measure the weight management knowledge of primary and secondary school students in China.