This Common Core Standards document, ELA and Literacy in Social Studies, Science, and Technical Subjects, Appendix A, includes an article on text complexity. It suggests that educators consider qualitative and quantitative factors along with and the reader and task when determing the complexity of a text.
This Lexile site will help you analyze the Lexile range of a book by measuring word frequency and sentence length. There is also access to a database of children's and young adult titles and their Lexile numbers.
Links to selected forms related to the Empire State Information Fluency Continuum. Click here for links to grade specific lesson planning forms and assessments.