| Ogre Enchanted | Levine, Gail Carson | Companion to Ella Enchanted | Fourth Grade, |
| Oh My Gods!: A Look-it-Up Guide to the Gods of Mythology | Bryant, Megan E. | Mythlopedia | Fifth Grade, |
| Oh Say Can You Say Di-no-saur? | Worth, Bonnie | Cat in the Hat Learning Library, The | First Grade, |
| Oh Say Can You Say What’s the Weather Today? | Rabe, Tish | Cat in the Hat Learning Library, The | First Grade, |
| Oh Say Can You Seed? | Worth, Bonnie | Cat in the Hat Learning Library, The | First Grade, |
| Oh Say, I Can’t See | Scieszka, Jon | Time Warp 'Trio | Fourth Grade, |
| Oh the Pets You Can Get: All About Our Animal Friends | Rabe, Tish | Cat in the Hat Learning Library, The | First Grade, |
| Oh The Things You Can Do That Are Good For You! | Rabe, Tish | Cat in the Hat Learning Library, The | First Grade, |
| Oh, the Places You’ll Go | Seuss, Dr. | | First Grade, |
| Oh, the Things They Invented!: All About Great Inventors | Worth, Bonnie | Cat in the Hat's Learning Librar | First Grade, |
| Oh, the Thinks You Can Think | Seuss, Dr. | | First Grade, |
| Okay for Now | Schmidt, Gary | | Secondary, |
| Old Hat New Hat | Berenstain, Stan & Jan | | Kindergarten, |
| Old Henry | Bios, Joan W. | | First Grade, |
| Old MacDonald Had a Boat | Goetz, Steve | | Kindergarten, |
| Old MacDonald Had a Truck | Goetz, Steve | | Kindergarten, |
| Old MacDonald’s Things That Go | Clarke, Jane | | Kindergarten, |
| Old Yeller | Gipson, Fred | | Fifth Grade, |
| Old-Fashioned Girl, An | Alcott, Louisa May | | Secondary, |
| Olive’s Ocean | Henkes, Kevin | | Secondary, |
| Oliver Twist | Dickens, Charles | | Secondary, |
| Omega Rising | Carman, Patrick | Voyagers; 3 | Fifth Grade, |
| On Beyond Bugs! | Rabe, Tish | Cat in the Hat Learning Library, The | First Grade, |
| On Beyond Zebra! | Seuss, Dr. | | First Grade, |
| On Market Street | Lobel, Arnold | | Kindergarten, |
| On My Honor | Bauer, Marion Dane | | Fifth Grade, |
| On the Banks of Plum Creek | Wilder, Laura Ingalls | Little House; 4 | Fourth Grade, |
| On the Far Side of the Mountain | George, Jean Craighead | | Fifth Grade, |
| On the Road to Mr. Mineo’s | O'Connor, Barbara | | Fourth Grade, |
| On to Oregon | Morrow, Honore | | Secondary, |
| Once Upon a Crime | Buckley, Michael | Sisters Grimm; 4 | Fifth Grade, |
| Once upon a Mastodon: All About Prehistoric Mammals | Worth, Bonnie | Cat in the Hat's Learning Library | First Grade, |
| One and Only Bob, The | Applegate, Katherine | One and Only Ivan; 2 | Sixth Grade, |
| One and Only Ivan, The | Applegate, Katherine | | Sixth Grade, |
| One Cent, Two Cents, Old Cent, New Cent | Worth, Bonnie | Cat in the Hat Learning Library, The | First Grade, |
| One Day in the Eucalyptus, Eucalyptus Tree | Bernstrom, Daniel | | Kindergarten, |
| One False Note | Korman, Gordon | 39 Clues (original); 2 | Sixth Grade, |
| One Fish, Two Fish, Red Fish, Blue Fish | Seuss, Dr. | | Kindergarten, |
| One Giant Leap | Burleigh, Robert | | Third Grade, |
| One Good Thing about America | Freeman, Ruth | | Fourth Grade, |
| One Hundred Days (plus one) | McNamara, Margaret | | First Grade, |
| One Hundred Shoes | Ghigna, Charles | | First Grade, |
| One Hungry Monster: A Counting Book in Rhyme | O'Keefe, Susan Heyboer | | Kindergarten, |
| One Plastic Bag : Isatou Ceesay and the Recycling Women of the Gambia | Paul, Miranda | | Second Grade, |
| One-eyed Cat | Fox, Paula | | Fourth Grade, |
| One… Two… Three… Sassafras! | Murphy, Stuart J. | | Kindergarten, |
| Onion John | Krumgold, Joseph | | Fourth Grade, |
| Only Game, The | Lupica, Mike | Home Team; 1 | Sixth Grade, |
| Only the Good Spy Young | Carter, Ally | Gallagher Girls; 4 | Secondary, |
| Open Boat, The (short story) | Crane, Stephen | | Secondary, |
| Operation Red Jericho | Mowll, Joshua | Guild of Specialists Trilogy; 1 | Secondary, |
| Operation Storm City | Mowll, Joshua | Guild of Specialists Trilogy; 3 | Secondary, |
| Operation Typhoon Shore | Mowll, Joshua | Guild of Specialists Trilogy; 2 | Secondary, |
| Ophelia and the Marvelous Boy | Foxlee, Karen | | Fifth Grade, |
| Orange Outlaw, The | Roy, Ron | A to Z Mysteries (original) ; 15 | Third Grade, |
| Original Beatrix Potter Tales | Potter, Beatrix | | First Grade, |
| Orion and the Dark | Yarlett, Emma | | First Grade, |
| Orphan Eleven | Choldenko, Gennifer | | Sixth Grade, |
| Othello | Shakespeare, William | | Secondary, |
| Other Side, The | Woodson, Jacqueline | | Second Grade, |
| Otis Spofford | Cleary, Beverly | | Fourth Grade, |
| Our Only May Amelia | Holm, Jennifer L. | | Fifth Grade, |
| Our Sacred Honor | Carter, Ron | Prelude to Glory; 1 | Secondary, |
| Our Solar System | Jackson, Tom | Magic School Bus Presents (Nonfiction Companion to The Magic School Bus Lost in the Solar System) | Third Grade, |
| Our Solar System | Simon, Seymour | | Third Grade, |
| Our Strange New Land | Hermes, Patricia | Elizabeth's Jamestown Colony Diary; 1 (My America) | Third Grade, |
| Out of my Mind | Draper, Sharon M. | | Sixth Grade, |
| Out of Sight Till Tonight!: All About Nocturnal Animals | Rabe, Tish | Cat in the Hat's Learning Library | First Grade, |
| Out of Sight, Out of Time | Carter, Ally | Gallagher Girls; 5 | Secondary, |
| Out of the Dust | Hesse, Karen | | Fifth Grade, |
| Outback All-Stars | Earhart, Kristin | Race the Wild; 5 | Third Grade, |
| Outcast of Redwall, The | Jacques, Brian | Redwall; 8 | Sixth Grade, |
| Outcasts, The | Flanagan, John | Brotherband Chronicles ; 1 | Secondary, |
| Outer Space | Jennings, Ken | Ken Jennings' Junior Genius Guides | Sixth Grade, |
| Outfoxed | Twohy, Mike | | Kindergarten, |
| Outside Dog, The | Pomerant, Charlotte | | Second Grade, |
| Outsiders, The | Hinton, S.E. | | Secondary, |
| Over and Under the Pond | Messner, Kate | | Kindergarten, |
| Over and Under the Snow | Messner, Kate | | Kindergarten, |
| Over in the Meadow | Keats, Ezra Jack | | First Grade, |
| Over Sea, Under Stone | Cooper, Susan | Dark is Rising Sequence, The; 1 | Sixth Grade, |
| Over the Moon | Lloyd, Natalie | | Fourth Grade, |
| Overboard! | Johnson, Terry Lynn | Survivor Diaries | Fourth Grade, |
| Overview, Young Explorer’s Edition: A New Way of Seeing Earth | Grant, Benjamin | | Secondary, |
| Owen | Henkes, Kevin | | Kindergarten, |
| Owl Moon | Yolen, Jane | | First Grade, |
| Owls | Marsh, Laura | National Geographic Readers: Level 1 | First Grade, |
| Ox-Cart Man | Hall, Donald | | First Grade, |
| Ozma of Oz | Baum, L. Frank | Wizard of Oz; 3 | Fifth Grade, |
| P.J. Funnybunny Camps Out | Sadler, Marilyn | | Kindergarten, |
| P.J. Funnybunny’s Bag of Tricks | Sadler, Marilyn | | Kindergarten, |
| Paddington | Bond, Michael | Paddington Treasury | Kindergarten, |
| Paddington Abroad | Bond, Michael | Paddington | Third Grade, |
| Paddington and the Marmalade Maze | Bond, Michael | Paddington Treasury | Kindergarten, |
| Paddington at the Beach | Bond, Michael | Paddington Treasury | Kindergarten, |
| Paddington at the Palace | Bond, Michael | Paddington Treasury | Kindergarten, |
| Paddington at the Zoo | Bond, Michael | Paddington Treasury | Kindergarten, |
| Paddington at Work | Bond, Michael | Paddington | Third Grade, |
| Paddington Goes to Town | Bond, Michael | Paddington | Third Grade, |
| Paddington Helps Out | Bond, Michael | Paddington | Third Grade, |