Fundamental Movement Skill (FMS) proficiency is an important antecedent of physical activity for children and adolescents. Many studies report children’s overall FMS proficiency to be low. However, in order to develop effective intervention strategies, it is critical to understand FMS proficiency at a behavioral component level. This study investigated British primary school children’s FMS proficiency across all three FMS domains, reporting proficiency at both an individual skill level and at a behavioral component level. Participants were 219 primary school children, aged 7–10 years (Boys 111, girls 108) from central England. We assessed (a) eight FMS (run, jump, hop, skip, catch, overarm throw, underarm throw, stability) using the second and third revisions of the Test of Gross Motor Development, and (b) stability, using the rock skill from the Rudd stability assessment tool. We calculated descriptive statistics and frequencies for each FMS and their behavioral components. We explored gender differences using the Mann- Whitney U-test, and differences between school years using the Kruskal- Wallis test. There was a similar pattern in the prevalence of failure for behavioral components across skills, with children failing on components requiring (a) the simultaneous use of both upper and lower limbs and (b) contralateral actions. Detailed descriptive analysis of low proficiency levels highlighted co ordination and the process for power/force production. These data can be used to guide development and plan targeted interventions for the weakest skills and behavioral components of 7-10 year old British primary school children to increase their FMS levels.