Purpose: To determine the accuracy of three systematic observation (SO) tools to estimate energy expenditure (EE) using different skill performance and observation intervals. Method: Three SO tools (Observational System for Recording Physical Activity in Children-Preschool, System for Observing Fitness Instruction Time, and System for Observing Play and Leisure Activity in Youth) were used to observe children (N = 42, M[subscript age] = 8.1 ± 0.7) during motor skill testing sessions. EE was measured using indirect calorimetry (COSMED K4b2). Results: Paired samples t tests, repeated-measures analysis of variance, and regression analyses were performed to compare the EE estimated from SO tools with EE measured by indirect calorimetry. The average mean difference between the estimated metabolic equivalence of task (METS) and actual METS ranged between -1.24 METS (SD = 1.62, p < 0.01) and -3.46 METS (SD = 1.31, p < 0.01) depending on skill performance interval or SO tool analyzed. Conclusions: SO tools did not accurately estimate EE during object control skill testing sessions. Physical educators should consider utilizing discrete motor skill practice to accumulate health-enhancing levels of physical activity while adhering to national standards.