Joe Bower posted some links about assessment onhis blog. He's pretty radical and espouses a view that assessment should be about helping the student learn - not a formal outcome.
You say you want this, so then why are you doing that?
Grading: Where do I stand?
My de-grading philosophy Q & A
The day I abolished Grading
Real learning is found in children not data
Working with Parents to Abolish Grading
No Good Reason to Grade
What leads to success?
Information vs Reward & Punishment
Detoxing children from grade-use
No Grades & Group Work
Should Students be paid to learn?
Intrinsic Motivation and Autonomy
Grades are Distracting
Multiple Choice Tests Suck