Generally, the Easy Book Collection (labeled E in the catalog) contains picture books, chapter books, and non-fiction books for early readers:
The Non-fiction (Dewey Decimal #s) Collection:
and Fiction (F) Collection:
both contain books for upper elementary through high school. Search Research@UWW for the topic of interest, then filter your search to a specific location (Curriculum Collection, Easy Books, etc.).
Given that a particular children’s book may be appropriate for a range of grade levels, and reading level information is not often included in Research@UWW for most children’s books, you will need to use a database to identify whether a particular item matches the grade level you are seeking. See this LibGuide page for Identifying Reading or Grade Level to find leveling information for a particular book. You could also choose to start by searching one of those databases on the LibGuide to identify a list of titles for a specific grade level, and then search Research@UWW to see whether we have a copy.