The Common Core State Standards for English Language Arts and Literacy (CCSS-ELA) were adopted by approximately forty states (though in some cases, with significant revisions). However, researchers are still trying to understand how teachers are implementing the CCSS-ELA at the ground level--that is, in actual ELA classrooms. The CCSS-ELA call for three big "instructional shifts" that are intended to address widely recognized and longstanding weaknesses in ELA instruction: First, they challenge teachers to engage students in "regular practice with complex texts and their academic language." Second, they urge them to sharpen their focus on "reading, writing, and speaking grounded in evidence from texts, both literary and informational." Finally, they encourage teachers to devote more attention to "building knowledge through content-rich curriculum." These are major changes to deep-seated and widespread practices, so nobody should assume that their implementation will be easy or automatic. This report seeks answers to three questions: (1) How are teachers interpreting the instructional shifts? (2) Are these shifts actually occurring? and (3) Where do teachers need more support to implement the shifts faithfully? [Written with Ann M. Duffett. Foreword and executive summary by Amber M. Northern and Michael J. Petrilli.]