The fact that Regents are a requirement means that Yeshivos have to teach at least SOME of the subject matter. I can only imagine just how little of anything would be taught if schools prepared their own final exams. That kids decide they cant cram for the exam, the week before the regent is not a fault of the exam. It is the fault of students who choose to do nothing the entire school year, yeshivos that feel it is a waste of time to hire competent teachers (and where there are competent teachers fails to instill a level of seriousness for “english” that learning the subject matter requires)and apathetic parents who allow both to get away with it.
If you want to argue whether standardized tests in general (under any name) are an indication of a students progress, how well the subject matter is taught and how well a school is doing, thats a different argument.