From a colonial standpoint this is really really interesting. I mean, personally I grew up reading all those Enid Blyton school stories (we'll talk about cultural appropriation and sanitisation and completely clueless racist subtext later) and always wondered what the hell 'fifth form' and the like meant. Conversely it's amazing how within a hundred years or so, the system at home has completely morphed into another beast altogether, though we're still taking our own versions of O and A Levels.