Most American students read Chaucer in high school. I would expect the Brits to know their own lit.
Don’t get much Chaucer in most “high schools” (i.e. their equivalents) here. At least I didn’t. Dickens and Shakespeare was mostly it.
Apart from the fact that English teaching isn’t great in the UK, it’s a product of the different system. I believe we get Chaucer at A-Level (which is what your high schools go to I think), but you only study a few A-Levels, if at all. Mine were all science or maths.