Common Core has expanded the Lexile levels in their standards, giving teachers who are being required to use the Lexiles more flexibility in their choice of books. The change was slipped into the fairly new publication, "Supplemental Information for Appendix A of the Common Core State Standards for English Language Arts and Literacy: New Research on Text Complexity" found at
You'll find the expanded Lexiles on page 4 of that document along with other reading formula levels by grade band. The footnote explains that, "This change was provided in response to feedback received since publication of the original scale (published in terms of the Lexile® metric) in Appendix A." To my mind, this is one more indication that the standards were rushed out without being tested.
At some point, the Common Core website added a "Myths vs. Facts" page in answer to questions and complaints. Ironically, there are some myths slipped in as facts. For example, it says of Appendix B, "The exemplars of high quality texts at each grade level provide a rich set of possibilities and have been very well received." I've searched "Appendix B" extensively on the Internet and I haven't seen one place where it was "very well received." Not surprising, since it recommends Little Women as a text for middle school (at what school?) and Russell Freedman's Lincoln: A Photobiography as a good read-aloud for second and third grade (a great book for middle school, not a read-aloud for second and third grade). Find the Myths vs. Facts page here: http://www.corestandards.org/about-the-standards/myths-vs-facts