A stroke of luck

"The big marking experiment" (18 September) raises the following questions. The reported span among grades may be encouragingly narrow, but those differences might matter all the more in a finely calibrated system, for example the American alphabetical scheme (A, A-, B+ and so on). Even if reliability among graders were relatively high, a system beset by grade inflation would merely yield reliably overstated grades. But just the same, one must laud an inquiry into grading inspired by a professor named Martin Luck.

Abbott Katz, London.