Additional follow-up of the ‘eligible sample’ has been made through school-administered questionnaires and assessments completed by the child’s teacher. There have been numerous subpopulation studies using quantitative and qualitative methodologies that are described later in this article. The ‘eligible sample’ have been linked to National Health Service (NHS) death and cancer registries (99% linkage match rate) and education attainment and school census data (82% linkage match rate, reflecting that only English GME schools are available; this excludes private education that has a 15.7% coverage locally). Both the participant's home and school addresses have been geocoded to a national reference table,8 which allows onward linkage to neighbourhood socio-demographic and environmental exposure indicators.
