This study tested the feasibility of using an inertial measurement unit to discriminate different developmental levels of children performing the standing long jump (SLJ). Sixty-four children (54.6% boys, 46.4% girls) aged 8 to 11 years old (M = 9.17, SD = 0.97) performed the SLJ three times and were classified by rater observations into three developmental levels. Concurrently, they wore an inertial measurement unit from which a set of temporal and kinematic parameters for the quantitative assessment of their jumps. A multivariate analysis of variance revealed that variability among the developmental groups was identified by the overall set of parameters, while discriminant function analysis verified that these parameters discriminated among developmental levels. Primary predictors for developmental group discrimination were maximum peak acceleration in the vertical and anteroposterior directions, respectively, and normalized preparation time. These outcomes represent significant steps toward improving the assessment of SLJ rate of development in childhood and supporting physical education.