The K-12 Common Core State Standards (CCSS) in mathematics and English Language Arts were developed through a state-led process managed by the National Governors Association (NGA) and the Council of Chief State School Officers (CCSSO).  Achieve partnered with NGA and CCSSO on the Initiative. Achieve (in partnership with the CCSS mathematics writing team) convened a group of experts to develop Model Course Pathways in Mathematics based on the Common Core State Standards. The Model Course Pathways in Mathematics are published as Appendix A to the CCSS.  Four model course pathways were created, each of which is intended to significantly increase the coherence of high school mathematics courses. Read the Model Course Pathways in Mathematics: http://cadrek12.org/sites/default/files/CCSSIMathematicsAppendixA.pdf