Here are a few research articles to help you understand my rationale behind using proficiency grading in my classroom:
7 Reasons For Standards-Based Grading
Grading What Matters
Praise For Proficiency
The amalgamation of many key points in these and other articles, along with talking to other teachers who have practiced proficiency grading, have helped form the system I use in my classroom. I constantly reflect on this system and make changes as needed, striving to make it the best it can be for the students.