After watching this film, I can say that it was really like no other movie I've ever seen before: in the "More Like This" section, I've tagged three of my faves (Dead Poets Society and School Ties) and a classic (The Prime of Miss Jean Brodie) as being similar, but I think they are only important as touchstones when trying to talk about this film, because it undoes a lot of the cliches of the "[Boarding] School for Boys" and/or "Great Teacher Movie" genre.
More than any similarly-minded films, The History Boys is about the students and not the teacher(s). In fact, making sure that there were four very different authority figures went a very long way to providing countless curious situations that, though not properly "exciting", were certainly exciting for the attempted anticipation of the results. It was kind of like a geneticist's punnett square: if this mixes with this, then we'll have this outcome... and if this meets that, then we'll have that outcome...
This was a very cerebral movie as well: accessible for its compassionate portrayal of eight young men and their intellectual (and sexual) awakenings, not to mention teachers equally on the upswing (Irwin) and downswing (Hector) of their careers, the film also says a great deal about history that I'm sure only my history-major friends could appreciate as schools of thought and epistemological theory related to "how to study" history. (Luckily, my background in literature studies helped me to at least understand Hector and his outmoded style of studying and teaching poetry.)
The historian Hayden White, for example, talks of the "emplotment" necessary when writing history. To recount a factual history, one must turn it into a narrative: Neville Chamberlain spoke for the appeasement of Adolf Hitler, which led to his consolidation of power, which led to the Second World War (etc.) - all narratives must have a sequence of events that makes sense, otherwise it's hard to accept the story. One paints some events as turning points, but they may be completely insignificant; as one of the boys in the film points out, Halifax was much more likely to become Prime Minister than Winston Churchill, but went to the dentist on the wrong day. If Halifax had had better teeth, would the war (and everything since) have turned out the same way? Who knows?
The discussion of history as "turning points", and it's contrasting characterization (from the supposedly dull boy, Rudge) as "just one thing after another" is a discussion that can be applied to the plot itself, which is the true brilliance of this film... looking back on the many contrasting moments, one has to ask oneself how the narrative worked: why the story was told the way that it was, and which moments (if any) are turning points? Is there a cause and effect relationship, or is this just one event stacked on top of another?
The film's ability to keep you hanging on insignificant plot points is a triumph, because you too must wait and see if, in the end, this moment will be a turning point. You'll reach the end, and you'll make a mental list, but you'll want to check it again by watching the moments unfold to see if they cause the ensuing events or merely precede them.
An excellent movie to purchase and watch over and over again, whether you've heard of Richard Rorty or not, the film carries a lot of its devices honed in the theatre (it's an adaptation of a play) onto the big screen, and is one that leaves many impressions on many levels... any of which, of course, may or may prove to be significant when one looks back on it the future.