Following an Edmonton teacher's suspension for "ignoring his principal’s repeated directions to follow the school’s no-zero grading practice", there has been a lot of discussion about assessment. I just wanted to link here to a couple of blogs that I think best express opinions from educators who are using assessment properly.
Zero-Knowledge Proofs by John Scammell
for the love of learning by Joe Bower
Teaching on Purpose by Cherra-Lynn Olthof
For the most part I agree with them, so it's easier to link to them than to re-invent the wheel.