In my quest to find unbiased research (as in not paid for by some organization that financially benefits from the PBE restructuring of our schools), I’ve run into a few pieces that shed a bit of a light. Unsurprisingly, most of them specifically mention that there’s no real evidence-based research showing the supposed benefits of standards, competency or proficiency-based education. Often, what is shared (and sometimes posed as a success story) is anecdotal and not necessarily something that is easily replicated — because each student, each teacher, each school, each school district (especially here in Maine) is unique.
COMPETENCY-BASED EDUCATION: An Overview for Michigan’s Superintendents (Source: http://piedmontpen.com/CBE_Final.pdf) — Maine is cited throughout
https://tultican.com/2018/02/14/standards-based-education-reform-is-toxic/ — Not a research paper, but an article that cites quite a lot of other education research