Here's some qualifiers:
Data for the figures presented in the final dimension were also taken in the majority from Currie, C., et al (eds) (2004) ‘Young People’s Health in Context. Health Behaviour in School-age Children Study’(HBSC): International report from the 2001/2002 study, WHO Regional Office for Europe. Figures 6.1, 6.2 and 6.3a are all derived from this source, and as such UK and Belgian results are to be treated with
caution (See note on Figure 1.3a).
Figure 6.3b is sourced from the OECD PISA survey 2003 accessed at http://
pisaweb.acer.edu.au/oecd_2003/ oecd_pisa_data.html in August 2005. UK results
should be treated with caution. The United States did not provide responses to these items.
And here is why:
The uncertainties surrounding the sample and its bias are such that PISA 2003 scores for the United Kingdom cannot reliably be compared with those of other countries. They can also not be compared with the performance scores for the United Kingdom from PISA 2000. The regional data from Wales are also not comparable with other countries.