Pisa is criticised for extrapolating from sparse data to unreliable results. Well, that is nothing compared with your leap from the comment of one, unnamed ministry official of unstated rank to the standfirst “India blames cultural bias for withdrawal from global study”. (“Poor performers pull out of Pisa”, 29 November). As the Organisation for Economic Cooperation and Development suggested, the reasons for India’s reluctance to participate in Pisa 2015 were many and varied. They included the cost, the difficulty of meeting Pisa’s rigorous quality standards (both Himachal Pradesh and Tamil Nadu states failed to meet the sampling criteria in 2010) and, may I suggest, the inevitable embarrassment of scoring far below the country’s regional competitors - even without any “cultural bias”. I can only presume that you played down the alternative explanations because they didn’t fit with the TES campaign to rubbish large-scale international assessments in general and Pisa in particular.

George Bethell, Director, Anglia Assessment.