The aim of this study was to develop, test, and employ an audit tool to objectively assess the opportunities for physical activity within school environments. A 44 item tool was developed and tested at 92 primary schools in the county of Norfolk, England, during summer term of 2007. Scores from the tool covering 6 domains of facility provision were examined against objectively measured hourly moderate to vigorous physical activity levels in 1868 9-10 year old pupils attending the schools. The tool was found to have acceptable reliability and good construct validity, differentiating the physical activity levels of children attending the highest and lowest scoring schools. The characteristics of school grounds may influence pupil's physical activity levels.