Adequate proficiency at object control skills, which is influenced by biological and environmental constraints, underlies the development of more complex sport-specific skills. This study describes proficiency at six object control skills and demographic correlates associated with each skill and each skill criteria in 9- to 10-year-old children who were randomly selected from 20 schools (N=826) and tested with the Test of Gross Motor Development-2. Cross-tabulation and hierarchical linear models were used to analyze the effects of sex (433 boys, 393 girls), ethnicity (619 Black, 207 White), and high (n=312) and low (n= 514) socioeconomic school environments. Twenty-three percent of the sample showed below average proficiency. Significant sex and socioeconomic school environment differences were found favoring boys and children from higher socioeconomic environments, although kicking showed significant interaction effects. It is concluded that environmental opportunities are the primary cause of differences across skills and the rates at which the skills are learned.