That as many students might have failed this year as last doesn't mean that you know *which*. And choosing the ones who fail clearly isn't the right approach, especially when in order to do so students had to be downgraded from a Teacher-assessed grade of C or even B. Calling the teacher grades "guesses", however, is a little derogatory. Although they were likely to be optimistic, they would at least in most cases have been based on actually assessing what the student had done in the last 18 months, and therefore be based on more information.
// ... the best attempt is achieved by taking all available data into condideration. //
That leads to another point that I've raised already, namely that recent education policy has, in effect, destroyed all reasonable data sources that there previously existed. In the days of Coursework, modular exams, AS Levels as an automatic first step to A Levels, etc, then losing the end of year exam season would not have been nearly such a disaster, because the Students would already have completed a good deal of their assessed course. The irony is that these were scrapped not because of pressure from teachers but because of Tory concerns about grade inflation. How ironic that their attempt to deal with this problem has indirectly contributed to the largest rise in top grades ever.
This point will, presumably, be ignored, and, besides, yet another upheaval in the exam system in such a short space of time would be disruptive. Still, if Williamson wants to rescue his reputation, then maybe actually doing something, rather than waiting for stuff to happen and then reacting, would be a good way of doing it. I suppose above I am implying that the right way to address the problems would be to scrap the idea of a single set of end-of-course exams -- a suggestion that would in effect undo the entire Tory education policy of the last decade. But maybe Williamson will think of something else to do that is as effective or more so. Or not. But it's his job, not mine.