"The difference between assessment of learning and assessment for learning is a crucial one, in many ways indicative of an important shift in education.
Traditionally, tests have told teachers and parents how a student "does," then offers a very accessible point of data (usually percentage correct and subsequent letter grade) that is reported to parents as a performance indicator.
Class data can be gathered to imply instructional effectiveness, and the data from multiple classrooms can be combined to suggest the performance of an entire school, but a core message here is one of measurement and finality: this is how you did. This was the bar, and you either cleared it or you didn't.
And it's all past tense."