Call me cynical, to me this sounds like a story so outrageous that it becomes rather implausible. Of course it's possible that there is a teacher who for several weeks/months says 'looks good, go for it' and then out of the blue, at the end, decides to do a 180, fails the students and says 'I'm failing you because I don't understand'. But despite me knowing quite a few idiots and incompetent people, that just doesn't sound very much like something that would really happen in the way it is being painted.
Of course I don't know the student, so I'm not going to go out and say that he's a liar, either. But there is room between calling somebody a liar and word for word believing a random stranger on the internet.
Which is why I commented that in these cases, I'd prefer to hear the other side of the story, rather than using an obviously colored view as 'proof' for the article's author preconceived notions.