An evaluation of the National Healthy School Standard (NHSS) was undertaken by the authors on behalf of the Department of Health and the Department for Education and Skills. One part of the evaluation involved gaining access to a number of datasets derived from previous research and analysing the health-related outcomes of schools which had attained Level 3 of the NHSS, compared with those of other schools. The sources which provided the most interesting findings were the Health-Related Behaviour Questionnaire (HRBQ) survey and the Ofsted database of school inspection ratings. This paper describes the statistical methods used, and the results of the HRBQ and Ofsted analyses. Using HRBQ data, many pupil-level outcomes were explored, but relatively few indicated significant differences and even those tended to be quite small. The Ofsted school-level data yielded stronger evidence of NHSS impact. The paper concludes by suggesting possible reasons for these findings.