Although not directly on the point of PPL examinations, I believe that the pre-entry test for a Flying instructor course should definitely include a written essay type examination paper, as this would give clear evidence of a candidate's ability to communicate and to construct a logical argument. This is tested nowhere in the training of pilots and given the lack requirement for any level of educational attainment, is probably a reason why some people find the examinations "difficult". If a minimum academic requirement was also a pre-requisite it would probably help to weed out some of the candidates who struggle.