Education Northwest has designed a series of rubrics that are grade-level appropriate. Google Education Northwest 6+1 Trait Writing. You will find a link to valuable rubrics ready to use in your classroom.
National Education Association has designed a series of rubrics that are grade-level appropriate, and have rubrics demonstrating how the 6 Traits of Writing Model supports the common core. To find this information google National Education Association 6+1 Trait Writing. There is a section on rubrics, and a section on linking Six Traits to the Common Core.