Smithsonian Little Explorers
This is a good introductory science series for your younger students. Each book is 32 pages and covers one broad topic. Books are divided into two-page spreads for each topic within. This keeps the information manageable and less overwhelming. Photos and illustrations are on every page for visual clarity of the topics. Information is put into terminology that makes sense to younger children. The back of the book includes a glossary of new words, critical thinking questions for discussion, and additional reading and internet resources.