iSuper Chinese Little Ph.D. Chinese Teaching Resources is an excellent series of science books for Grades K-5. Kids will be very intrigued by the beautiful photographs! In addition, the large Chinese characters make this series a great resource for budding readers.
Shapes Chinese Books 形状万花筒 is an excellent series of books for the budding reader. Large Chinese characters are on separate pages from the cute and clever illustrations that kids will love! Each story concludes with a positive message as well as full English translation and pinyin reference.
识字儿歌 (Shìzì er gē / Word Songs) is a set of illustrated nursery rhymes and workbooks accompanied by a CD. I highly recommend this for children who are starting to learn Chinese. The simplified Chinese text is printed clearly with pinyin below each word.
I highly recommend the DailyNoodles My Fun Chinese Numbers and Animals Books as a hands-on introduction to Chinese learning for kids. Included are fun crafts, coloring, matching games, Sudoku, Zodiac animals, and more!
National Geographic has two fantastic Solar System books for children in Chinese! 太空百科 is a perfect introduction to Outer Space while 13颗行星 would be a great resource for upper elementary students!