The NYSED’s response (source):
The basic argument is that the assignment of grades is subjective with no universal (standardized) method of how grade assignments occur at the local level. Here is a passage from a 2005 report to the Board of Regents (with a link to the document) as well as one from 2004.
February 2005 report (source):
"Combine course grades and Regents exams?" This is often what people mean by "multiple measures.” Averaging Regents exams and course grades is unsound because the work that draws an A in one school merits only a C in another. Grade inflation is a widely recognized problem. The Regents have a two-part requirement for graduation. Students must earn 22 credits that are awarded locally, and pass five Regents exams that meet a high statewide standard. There has always been a line between these two parts of the assessment system. To combine them crosses the line. Teachers know that averaging course grades and Regents exams would put enormous pressure on every teacher to raise grades. And how would averaging work? Would course grades count for 20%? 40%? And how would we decide? Where is the expert opinion based on evidence that would enable the Regents to make such a decision? Regents exams adhere to rigorous professional standards for test validity and reliability. Where is the comparable evidence for the exams devised locally? The course grades averaging idea is unworkable.
December 2004 report (source):
"…standards vary. The Education Trust has reported that work that draws an A in many low performing schools merits only a C in high performing schools. Regents exams, in contrast, represent a common measurement of achievement. While classroom exams and other course requirements are known to few beyond the classroom in most cases, the Regents exams are subject to universal public and professional scrutiny.”