I agree that this would make a good teaching point. And it's entirely possible that the high school Literature teacher did have such a discussion with the students. The article doesn't specify, so we don't really know.
But it bears repeating that the book was not banned, as the title of this thread erroneously claims. The book was taken off the school's required reading list. But it's still available in the school library. Students are welcome to read it at their leisure. They simply aren't required to read it anymore. And while this incident presented a teachable moment, there are plenty of other ways to impress upon teenagers why it's inappropriate to use the n-word.
This is sort of like when Christians complain that public schools have "banned" prayer or "banned" God. This isn't true either. Students are free to pray voluntarily in public schools. They simply aren't required to. If a student wants to quietly ask for divine guidance before his calculus final he is free to do so. If he wants to offer thanks to the Almighty for his goulash and tater tots at lunchtime, no principal is going to haul him out of the cafeteria by his ear.
Similarly, students at this high school are free to read Huck Finn if they so choose. They can borrow it from their school library. If it's already checked out then they can probably get a copy at a local public library or book store. If all else fails, they can download it to their phone or tablet for next to nothing. I bought the complete works of Mark Twain a few years ago for $1.99 plus tax. It's pretty much everything he ever published - novels, short stories, essays, etc. All for about the price of an order of french fries.
I bet the school would even allow students to form a study group or book club that reads and discusses Huck Finn.