There's some discussion on badscience about GCSE grade inflation. I was wondering whether shifts in the socioeconomic stucture of the UK could be driving some of the increase in GCSE results, and I was just about to get into some serious analysis of data from the Youth Cohort Study when I plotted this to get an idea of how likely the hypothesis was. Turns out not so likely after all - the increase in grades runs across all socioeconomic groups (SEG until 2000, then I included NS-SEC: Higher professional, Lower professional, Intermediate, Lower supervisory, Routine, and Other - which likely explains the inflexion points at 2000). This suggests that an incresing proportion of middle class kids, or improved attainment amongst working class kids is unlikely to explain the rise in GCSEs. Obviously, if you believe that IQ is a good unbiased measure of intelligence you might explain grade increases as the esult of the Flynn effect - the secular increase in IQ scores with each cohort. As I think that modern increases are largely a result of increased familiarity with IQ tests that option isn't open to me. But the large differences between different groups, presuming you don't think they are a result of the intellectual inferiority of the poor, suggests a very large role for social and cultural factors - and if these change over time this could have a large effect on overall grades. Now I'm not sure what these factors might be - motivation and parental assistance are obvious ones, but I think it is pretty likely that at least some of the current grade inflation could be explained by this - rather than exams getting easier, although I doubt anyone will choose to focus on that when the cheap headlines practically write themselves each year.