Replying to myself to add that that last ~10% is an enormous time-sink. You'll have to look up every unfamiliar word, which isn't a big deal for a short text, but becomes one for something longer. Worse, though, is that you'll constantly be led astray by words whose meanings have drifted over time: your interpretation (often) won't align exactly with that of Chaucer or his audience. What I said above is good enough for casual / undergraduate use - the stories are still funny, and / or have enough depth for a good discussion - but there's a reason "medievalist" is an actual speciality: you'll spend a whole career trying to get to 100%.

English nerd (and former English teacher) here, and I think for high school students that's a good idea. It's not actually an impossible text, and an introduction to the real thing is useful and interesting, but forcing teenagers to go through everything in the original is too much of an obstacle for most students.

Also: only reading the "boring" bits. When I was in high school I was excused English classes (took English 101 at the local college instead - told you I was a nerd), but overheard my classmates hating their way through "The Wife of Bath's Tale", or "The Knight's Tale" - one of those - and introduced them (nerd!) to "The Miller's Tale" - broad scatalogical comedy - which they loved. Later I did something similar for them with Gulliver's Travels, by showing them the bit where he has fairly graphic sex with the giantess. (I think that's an actual kink, but I certainly didn't know that at the time!)

Take a look at Frisian for the beginning of an answer.

https://en.wikipedia.org/wiki/Frisian_languages