Clarification Request on Grading

In talking about grading kids, Michele sent in this link:

http://prezi.com/axzlriy65i7x/daughertys-bicycles-performance-based-learning/

She was saying how at parents night, she uses this bike analogy applying the process of riding a bike to explain how she grades.

My response is that in my confused mind this conflicts with natural emergence of skills as per Krashen. A kid who is stable on the bike is labeled as a C student. The motivation and human level participation is not brought into the labeling of the kid as a C student. We have all sorts of kids in our classes with all sorts of abilities who learn at different rates of speed. The key factor is motivation – we know that. Some are highly motivated, and some are not. So I don’t see how labeling the kid where they are with being able to ride the bike is fair. Somebody explain this to me. I really don’t see how we can take one kid, label her as “beginning”, and then attach a grade range of 60% to 69% on this when she is trying. I can see how we can successfully label her involvement by using the jGR but not here. What am I missing? I’ll try to say it again, more clearly – we know that language skills emerge at different rates and at different points in a continuum that is personal to the kid’s skills. Some people speak earlier than others, for example. So the kid who starts speaking at age 3 gets an A but the kid who starts speaking at age 6, according to this scale, would then, at the age of 3, get an F. Is that it? Is that what the ACTFL proficiency guidelines offer us for our grade level designed instruction? If that is true, I don’t want to use the ACTFL guidelines to assess my kids. I want to assess their observable behaviors and how well they attempt to negotiate meaning with me and with what they read in my classroom. Do I have to use the proficiency guidelines as clarified by this bicycle analogy? Somebody work with me here. I apologize if my question is not clear, but I am not clear on the question myself. Something feels off on that bicycle image. The observable behaviors in terms of effort and the negotiation of meaning piece don’t seem to be present in the ACTFL comparison bike image. The human piece is missing. Or I am just off on this one? I don’t want to give A’s to the best bike riders. I want to give A’s to the kids who try the most. Is that bad?