Ofqual's A-level algorithm: why did it fail to make the grade?

There is a lot we can learn from the algebraic symbols used to determine results in England

• A university vice-chancellor's diary of A-level chaos

P_kj = (1-r_j)C_kj + r_j(C_kj + q_kj - p_kj)

For such a short string of algebraic symbols, there is a lot we can learn from Ofqual's grading algorithm (though really it is an equation) - and a lot we can learn about what went wrong.