First watch this video to the very end.
Okay, so you get the idea. Assessment for learning assumes that learning is a continuous process, and that using a final average of the student’s work can interfere with the important task of understanding students. An average only shows what could be expected of typical performance of a student and doesn’t show any of the trends in student learning.
In our IB MYP school, we use assessment for learning. Each time we are asked to produce a report card, we take a snapshot of what we think the student should be capable of doing by examining their current portfolio of work, and we record that snapshot as the grade. We don’t average grades. If a student starts out the beginning of the year and does nothing, but then by the end of the year they are producing masterpieces, then we assume that they can produce masterpieces. We all know the content at the end of the year is generally more difficult than the beginning of the year, but we also know that kids change during a year.
Let’s look at a more extreme analogy. Suppose you are trying to become a famous painter. You try and create a masterpiece, but over and over again your work just isn’t there. You keep improving a little bit each time because you are practicing, but most of what you produce is really not that good. One day you have a break-through and you paint a masterpiece. Your work goes viral and you make millions of dollars in prints. Are you successful? Should we consider a kid who produces an awesome piece of work to be successful? What if it is their final exam?