The Math Wiki provides detailed information about grade-level specific standards and, helpfully, examples of proficient responses for those standards. There are also pacing documents (called Scope and Sequence) to help you know what content is being taught when in ALL NC schools.
This is the consortium of universities, educators, school districts, etc. across the state who are responsible for the shifts in NC standards. Research supporting the shifts can be found here, as well as a grade-level specific framework detailing every standard.
This is THE site I strongly encourage you to visit if you want ANY information or research about the shifts in mathematical practices and the BEST ways in which children learn math. It is maintained by Jo Boaler and Stanford University. There are parent and student resources, as well as apps and games linked underneath the Tasks & More heading.
Do you ever wonder why content is taught in a particular order in math? These short videos highlight the progression in concepts such as addition, subtraction, multipplaction, division and fractions.