I came across this today and it's an interesting read. Unfortunately the authors take the attitude that high scorers "rode winning streaks to the top." It doesn't address the problems that can occur when high scorers aren't given challenging work.

On the other hand, there were a number of things that may be useful for advocacy. I included some excerpts:
http://www.assessmentinst.com/forms/AssessManifesto-08.pdf
Quote
For instance, the assessment
results must go beyond merely providing judgments about
to providing rich descriptions of student performance. In
other words, if assessments are to support improvements
in student learning, their results must inform students how
to do better the next time.


Assessments become far more than merely
one-time events attached to the end of the teaching.
They become part of the learning process by keeping
students posted on their progress and confident enough
to continue striving.

We assess for two reasons: (1) to gather evidence to
inform instructional decisions and (2) to encourage
students to try to learn. Both purposes must be well
served for schools to be effective.


If assessment is to support learning as students
ascend the progressions, then, it must serve as follows:
� Decision to be made:
What comes next in the learning?
� Made by:
Students, teachers, and sometimes parents
� Information needed:
Continuous evidence of each student�s current
location on the scaffolding leading to each standard

And, note that the question is not: Who is mastering
standards? Rather, it is: How is each student doing on
her or his journey up the scaffolding leading to each
standard?

Assessments become far more than merely
one-time events attached to the end of the teaching.
They become part of the learning process by keeping
students posted on their progress and confident enough
to continue striving.