Every year the Iowa Association of School Librarians assembles four lists of books based on grade level. The Iowa High School Book Award is for 9th through 12th grade. Students in those grades who read books from the list can vote for the award winner. Student must read at least two books from the list to be able to vote.

More details can be found here: https://www.iasl-ia.org/awards/book-awards/iowa-high-school-book-award-9-12