It is empirically demonstrated that adjusting aggregated measures of either student or school performance to account for the relative difficulty of General Certificate of Secondary Education (GCSE) subjects makes essentially no difference. For either students or schools, the correlation between unadjusted and adjusted measures of performance exceeds 0.998. This indicates that suggested variations in the difficulty of different GCSE subjects do not cause any serious problems either for school accountability, or for summarising the achievement of students at GCSE.