This list is by no means exhaustive, though tracking down all those reading levels was exhausting! I went looking for books that are at an end-of-fifth-grade reading level or higher, but that should be fairly acceptable for younger readers (sorry, no Hunger Games, and it's only a 5.3 anyway). I will continue to add to the list as more titles come to my attention.
Classics (like, older than Mrs. Murray)
Across Five Aprils, Irene Hunt 6.6
The Adventures of Sherlock Holmes, Sir Arthur Conan Doyle 5.7
*Alice in Wonderland, Lewis Carroll 5.7
*Anne of Green Gables, LM Montgomery 7.3
Around the World in Eighty Days, Jules Verne 9.6
Big Red, Jim Kjelgaard 5.6
*The Black Stallion, Walter Farley 6.1
Call it Courage, Armstrong Sperry 6.2
The Call of the Wild, Jack London 7.0
The Count of Monte Cristo, Alexander Dumas 8.8
Diary of a Young Girl, Anne Frank 6.5
The Hobbit, JRR Tolkien 6.6
The Incident at Hawk’s Hill, Allan Eckert 7.2
Ivanhoe, Sir Walter Scott 12.9
Johnny Tremain, Esther Forbes 5.9
The Jungle Book, Rudyard Kipling 7.5
Kim, Rudyard Kipling 7.7
The Legend of Sleepy Hollow, Washington Irving 11.0
*The Lion, the Witch, and the Wardrobe, CS Lewis 5.7
Little Princess, Frances Hodgson Burnett 5.5
Little Women, Louisa May Alcott 7.4
The Merry Adventures of Robin Hood, Howard Pyle 8.6
My Friend Flicka, Mary O’Hara 6.0
My Side of the Mountain, Jean Craighead George, 6.7
Peter Pan, JM Barrie 7.3
The Rescuers, Margery Sharp, 5.7
Robinson Crusoe, Daniel DeFoe
Roll of Thunder, Hear My Cry, Mildred Tylor 6.4
The Secret Garden, Frances Hodgson Burnett 6.2
Shane, Jack Schaefer, 5.5
Trouble River, Betsy Byars, 5.8
Tarzan of the Apes, Edgar Rice Burroughs 9.0
Treasure Island, Robert Louis Stevenson 6.0
Tuck Everlasting, Natalie Babbitt 5.9
The Trumpet of the Swan, EB White 5.9
20,000 Leagues Under the Sea, Jules Verne 10.0
War of the Worlds, HG Wells 6.5
The Wonderful Wizard of Oz, Frank Baum 7.0
The Yearling, Marjorie Rawlings 5.5
Past Newbery Medal/Newbery Honor Books
Caddie Woodlawn, Carol Ryrie Brink 6.0
Elijah of Buxton, Christopher Paul Curtis 6.0
Everything on a Waffle, Polly Horvath 5.9
Hattie Big Sky, Kirby Larson 6.3
The House of the Scorpion, Nancy Farmer 6.1
Lizzie Bright and the Buckminster Boy, Gary Schmidt 7.2
A Single Shard, Linda Sue Park 6.8
The Thief, Megan Whalen Turner 6.0
The Voice that Challenged a Nation: Marian Anderson and the Struggle for Equal Rights, Russell Freedman 7.3
Contemporaryish (like, younger than Mrs. Murray)
Al Capone Does my Shirts, Gennifer Choldenko 6.5
* Animorphs (series), Katherine Applegate, 5.7+
The Castle Corona, Sharon Creech, 5.5
A Crooked Kind of Perfect, Linda Urban 6.3
The Cryptid Hunters, Roland Smith, 6.8
*The Dark is Rising, Susan Cooper 6.2
*Eragon, Christopher Paolini, 5.8
The Evolution of Calpurnia Tate, Jacqueline Kelly, 7.5
From the Mixed-Up Files of Mrs. Basil E Frankweiler, EL Konigsburg 5.6
The Giver, Lois Lowry, 6.8
Gregor the Overlander, Susanne Collins 6.0
*Hatchet, Gary Paulsen 5.7
Holes, Louis Sachar, 6.5
*How to Train Your Dragon, Cressida Cowell 6.0
The Iron Trial, Cressida Cowell and Holly Black 5.7
*The Mysterious Benedict Society, Trenton Stewart 5.6
*The Ranger’s Apprentice: The Ruins of Gorlan, John Flanagan 7.0 (maybe too violent for sensitive readers)
Regarding the Fountain, K. Klise and M Klise 5.8
*Redwall, Brian Jacques 5.6
*Sabriel, Garth Nix 7.3
Savvy, Ingrid Law, 6.0
*A Series of Unfortunate Events, Lemony Snicket, 6.0+
The Supernaturalist, Eoin Colfer 6.2
The Trouble with Tuck, Theodore Taylor 6.0
*Tuesdays at the Castle, Jessica Day George 5.8
The Witch of Blackbird Pond, Elizabeth George Speare 5.7
*The White Mountains, John Christopher 6.2
A Week in the Woods, Andrew Clements 6.3
*A Wizard of Earthsea, Ursula LeGuin 6.7
* part of a series
Classics (like, older than Mrs. Murray)
Across Five Aprils, Irene Hunt 6.6
The Adventures of Sherlock Holmes, Sir Arthur Conan Doyle 5.7
*Alice in Wonderland, Lewis Carroll 5.7
*Anne of Green Gables, LM Montgomery 7.3
Around the World in Eighty Days, Jules Verne 9.6
Big Red, Jim Kjelgaard 5.6
*The Black Stallion, Walter Farley 6.1
Call it Courage, Armstrong Sperry 6.2
The Call of the Wild, Jack London 7.0
The Count of Monte Cristo, Alexander Dumas 8.8
Diary of a Young Girl, Anne Frank 6.5
The Hobbit, JRR Tolkien 6.6
The Incident at Hawk’s Hill, Allan Eckert 7.2
Ivanhoe, Sir Walter Scott 12.9
Johnny Tremain, Esther Forbes 5.9
The Jungle Book, Rudyard Kipling 7.5
Kim, Rudyard Kipling 7.7
The Legend of Sleepy Hollow, Washington Irving 11.0
*The Lion, the Witch, and the Wardrobe, CS Lewis 5.7
Little Princess, Frances Hodgson Burnett 5.5
Little Women, Louisa May Alcott 7.4
The Merry Adventures of Robin Hood, Howard Pyle 8.6
My Friend Flicka, Mary O’Hara 6.0
My Side of the Mountain, Jean Craighead George, 6.7
Peter Pan, JM Barrie 7.3
The Rescuers, Margery Sharp, 5.7
Robinson Crusoe, Daniel DeFoe
Roll of Thunder, Hear My Cry, Mildred Tylor 6.4
The Secret Garden, Frances Hodgson Burnett 6.2
Shane, Jack Schaefer, 5.5
Trouble River, Betsy Byars, 5.8
Tarzan of the Apes, Edgar Rice Burroughs 9.0
Treasure Island, Robert Louis Stevenson 6.0
Tuck Everlasting, Natalie Babbitt 5.9
The Trumpet of the Swan, EB White 5.9
20,000 Leagues Under the Sea, Jules Verne 10.0
War of the Worlds, HG Wells 6.5
The Wonderful Wizard of Oz, Frank Baum 7.0
The Yearling, Marjorie Rawlings 5.5
Past Newbery Medal/Newbery Honor Books
Caddie Woodlawn, Carol Ryrie Brink 6.0
Elijah of Buxton, Christopher Paul Curtis 6.0
Everything on a Waffle, Polly Horvath 5.9
Hattie Big Sky, Kirby Larson 6.3
The House of the Scorpion, Nancy Farmer 6.1
Lizzie Bright and the Buckminster Boy, Gary Schmidt 7.2
A Single Shard, Linda Sue Park 6.8
The Thief, Megan Whalen Turner 6.0
The Voice that Challenged a Nation: Marian Anderson and the Struggle for Equal Rights, Russell Freedman 7.3
Contemporaryish (like, younger than Mrs. Murray)
Al Capone Does my Shirts, Gennifer Choldenko 6.5
* Animorphs (series), Katherine Applegate, 5.7+
The Castle Corona, Sharon Creech, 5.5
A Crooked Kind of Perfect, Linda Urban 6.3
The Cryptid Hunters, Roland Smith, 6.8
*The Dark is Rising, Susan Cooper 6.2
*Eragon, Christopher Paolini, 5.8
The Evolution of Calpurnia Tate, Jacqueline Kelly, 7.5
From the Mixed-Up Files of Mrs. Basil E Frankweiler, EL Konigsburg 5.6
The Giver, Lois Lowry, 6.8
Gregor the Overlander, Susanne Collins 6.0
*Hatchet, Gary Paulsen 5.7
Holes, Louis Sachar, 6.5
*How to Train Your Dragon, Cressida Cowell 6.0
The Iron Trial, Cressida Cowell and Holly Black 5.7
*The Mysterious Benedict Society, Trenton Stewart 5.6
*The Ranger’s Apprentice: The Ruins of Gorlan, John Flanagan 7.0 (maybe too violent for sensitive readers)
Regarding the Fountain, K. Klise and M Klise 5.8
*Redwall, Brian Jacques 5.6
*Sabriel, Garth Nix 7.3
Savvy, Ingrid Law, 6.0
*A Series of Unfortunate Events, Lemony Snicket, 6.0+
The Supernaturalist, Eoin Colfer 6.2
The Trouble with Tuck, Theodore Taylor 6.0
*Tuesdays at the Castle, Jessica Day George 5.8
The Witch of Blackbird Pond, Elizabeth George Speare 5.7
*The White Mountains, John Christopher 6.2
A Week in the Woods, Andrew Clements 6.3
*A Wizard of Earthsea, Ursula LeGuin 6.7
* part of a series