What is it? Come get a preview of the newest book in BIE's PBL Toolkit series. It's a practical guide to building 21st century student competency in the "4 C's" -- critical thinking, collaboration, communication, and creativity/innovation. The book is designed for middle school and high school teachers, instructional coaches, and school leaders. It also shows how the 4 C's in a PBL context align with the Common Core State Standards.