Reading levels vary between publishers of children's books, with Scholastic using an alphabetical progression of guided reading levels from A to Z, correlated with school grade progressions from kindergarten to grade six. These reading levels overlap in places, such as between the first and second grades, where reading levels E through I are applicable to both. HarperCollins' imprint I Can Read! uses a different reading level scale, starting with "My VERY First" and "My First: SHARED READING" and progressing through levels 1 to 4.
Children's books in I Can Read!'s "My VERY First" category are illustrated and use only short, easily-comprehensible sentence structures. The next reading level, "My First SHARED READING" introduces additional albeit still simple vocabulary, still alongside illustrations. Level 1 books introduce more challenging vocabulary to maintain the child's interest, but continue to use familiar words and short sentences as well.
Level 2 books have more complex narratives and longer sentences, and Level 3 books incorporate interesting themes, plots and more challenging vocabulary for independent readers. Finally, Level 4 books are characterized by short paragraphs and chapters, assisting young readers in their transition to traditional chapter books.
Scholastic's reading level scheme is fairly straightforward to apply to children based on their school grade. I Can Read!'s reading levels, by contrast, require more intimate knowledge of a child's progress in reading.