"The Miller's Tale" represents a challenge for our young students: it gives them the story line that they really want (taboo, bawdy, "real"), but they have to talk about it in front of an adult. And not just any adult. They have to talk about sex, adultery, and butt jokes in front of their English teacher. Hence, there is often tension; at least, there is embarrassed silence. So, before you throw out the oh-so-uncomfortable "How about that Miller, eh?" consider their probable questions and the possibilities will blossom before you.
So, you've done the right thing and introduced "The Miller's Tale" by talking about the social milieu of this pilgrim, how he contrasts with the Knight (who tells the tale before him), and how the Miller's bawdy story fits into the genre of the French fabliau. In the end, though, who are you kidding? CHAUCER WROTE A DIRTY STORY! What a perve! While certain delicate students might want to block out this truth, most will take wicked delight in knowing that someone considered the Father of the English Language really took pleasure in creating these earthy stories.
The line to pursue: Why does Chaucer include this kind of person on his pilgrimage to a holy place? Why would he ever put these words into his pilgrim's mouth? By using the text of the "Prologue," most students will be quick to point out that Chaucer the Narrator distances himself as much as he can from the Miller's churlish behavior. Some will realize that this is only a fictional ploy for Chaucer the Poet to save face with his courtly audience while still writing the naughty story that he wants to write.