You asked why the teachers union is for it. I don’t know, ask your husband a retired school teacher. Nobody ever accused the teachers union – the uft – of keeping an agenda that had the best interests of the students as its goal. The agenda of the uft seems to be driven by what’s best for its members.
I took the regents. They were a lot easier than any test my teachers would have prepared (I went to a school where english was and is taken seriously). I don’t think they are any more or less useful or useless, depending on your point of view, than a final exam prepared by the teacher.