Oh yeah, Huck Finn or Tom Sawyer would be terrible for learning standard English. The protagonists are not well-educated. I used the Teachers First site as a guide (http://www.teachersfirst.com/read-sel.cfm) and checked the Grade 8 recommendations (this would be Junior High level, about 12-13 years old) and these are the ones we read in school that I think would work: The Red Pony (John Steinbeck) Rebecca (Daphne DuMaurier) - if you like mystery/gothic type novels A Separate Peace (John Knowles) A Night to Remember (Walter Lord) - about the sinking of the Titanic Not mentioned on the list is To Kill a Mockingbird (Harper Lee). There are a handful of episodes where less educated people speak and the language is transcribed (so it's a little difficult to understand), but overall, it's understandable and it's a book that pretty much all of us read in school. Little Women (Louisa May Alcott) and The Prince and the Pauper (Mark Twain) are also mandatory reading, but very dated, I think (as is Nathaniel Hawthorne's The Scarlet Letter).

Huck Finn is definitely an advanced book. I recommend some of the following books I read in elementary school: Harry Potter Series The Compound 39 Clues Diary of a Wimpy Kid (really easy)