In the process of educating physically literate individuals, physical educators are tasked with assessing health-related fitness of their students. It is essential to identify or develop appropriate field tests of muscular power for use in physical education settings. This study assessed jumping power in a sample of fourth, sixth, and eighth graders via a novel calculation method and compared different field tests and calculations for assessing muscular power. Participants (n = 99), aged 9 to 14 years, were recruited from fourth-, sixth-, and eighth-grade physical education classes in one K-8 school. Three jump measurements were taken within the context of a physical education class: vertical jump (VJ) via a Vertec device, counter movement jump (CMJ) based on flight time via MyJump iOS app, and standing long jump. Vertical jump scores assessed via the Vertec device were significantly greater than those for the CMJ. The mean power for participants in this study was 873 W for a CMJ and 1544 W for a VJ. Standing long jump only had a moderate correlation with power calculated from a CMJ (r = 0.41). Results confirmed that calculations of power that factor in VJ and body weight provide a better indication of power than does jump performance alone. The equation used to calculate jumping power offers a novel approach for physical education that is accurate and feasible.