Regular physical activity and supervised strength training are recognized components of healthy growth and motor development during childhood. Although linear and nonlinear periodized strength training are widely used approaches for organizing resistance training, limited information is available regarding their comparative application in school-aged children, particularly within school-based programs. This randomized controlled trial compares two periodized strength training models implemented over a 20-week intervention in schoolchildren to assess muscular power and speed/agility using standardized motor performance assessments.