Most teachers I know who are working to apply standards-based grading practices in the classroom have a struggle around what a "four" looks like. I have heard arguments that such a level is superfluous, and for the most part, I'm inclined to agree. If the kid can earn a three (i.e. meets standard), then isn't that the goal?
Someone recently pointed me toward a site for Highland Tech High in Anchorage, Alaska. Standards-based grading is the norm there and they have a unique way to define a level four performance. In order to earn a four (i.e. exceeds the standards), one student has to be able to teach another student to mastery. It is a variation on the old med school mantra of "See one, do one, teach one." I like this idea in the sense that it would require a student to have enough of a mastery of a concept that they would be able to apply it in a new context: another learner. I would guess that plenty of teachers have had the experience where you've tried to present/explain/explore a concept with kids...only to have one student pipe up and clear up the remaining confusion for peers. Sometimes learning takes a new way of looking at the information and as teachers, we can't always think of every possibility. My only concern with this model would be any added expectations of the "master" students. I have said over and over again that I do not believe kids should be teaching tools. However, there is a difference between requiring that a student tutor a peer and offering the option of developing their application of learning.
Would this option work for elementary students, too? It might. I think that at the secondary level, you could give more assessment responsibilities to the kids (How do you know that your classmate has met the standard?), younger children might not be ready. I have seen very young children teaching one another, so I think it's possible they might be recruited to help with letter naming or math facts---especially with a protocol. Here again, I struggle with whether or not this would look more like a requirement or an option. Is a first-grader really going to care about a four on their report card...or would a parent care more?
What do you think a four represents?