In the companion article based on ALSPAC mothers, comparisons of socio-economic characteristics between the original recruited ALSPAC mothers, mothers of a child of similar age living in Avon at the time of ALSPAC initiation and mothers living anywhere in the UK are shown.4 Here we present comparisons of demographic and standard school assessment data, typically taken at 16 years of age, between a national sample, the ALSPAC ‘enrolled sample’ and individuals with different enrolment, participation and study attrition histories (Tables 2–5). The data are taken from the National Pupil Database (NPD) ‘Key Stage 4’ (KS4) dataset, recording pupil census and assessment data for all pupils in English schools. Of these, 14 878 ‘eligible’ children have been linked to a subset of the NPD KS4 records that relate to government-maintained establishments (GMEs). As such, this offers the best available, yet not complete, comparison group (see footnotes in Table 2). Table 2A comparison of academic attainment between the national NPDa sample and ALSPAC children who have enrolled, have recently participated or are lost to follow-upALSPAC enrolment and current participation statusComparative indicatorNational NPD
