Between 1975, with the introduction of the national alphabetic grades to the O-Level, and the replacement of both the O-Level and CSE with the GCSE, in 1988, approximately 36% of pupils entered for a Mathematics exam sat the O-Level and 64% the CSE paper. With grades allocated on a normative basis with approximately ~53% (10% A, 15% B, 25–30% C) obtaining a C or above at O-Level, and 10% the O-Level C equivalent Grade 1 CSE; a proportion being entered for neither paper. The percentage of the population obtaining at least a grade "C" or equivalent in maths, at O-level, remained fixed in 22–26% band.