Hi Tom--how are things down there in Wolf Creek? Did you get any of that snow a couple days ago?
I don't know if the Stepping Stones concept is an extension of the Center Line Model (both PSIA trademarks), since the term "Center Line" does not appear in the manual at all. I do think it is a replacement, because it addresses similar concepts in what may be a simpler, easier to grasp form.
For those who are lost, the Center Line Model was PSIA's skiing model for the last 15 or so years. It described certain fundamental movements and tactics of contemporary offensive turns, and traced their development from the earliest stages of skill through expert, with four representative "milestones" along the way. The Center Line Model also identified other types of important movements, such as braking, defensive movements and pure-carving movements, and thus provided a sort of "map" of all of skiing's various technical and tactical options.
A key concept of the Center Line Model was the idea of Linear and Lateral Learning, both of which it encouraged instructors to be able to teach. Linear Learning means developing the same fundamental movements to a higher level of skill--moving "up" the Center Line toward the next milestone. It might mean, for example, helping someone who has skied a few days and is making basic parallel turns learn to become more "dynamic," with higher speeds, increased range of motion, higher edge angles, and thus more performance from the skis.
"Lateral Learning" means exploring DIFFERENT TYPES of movements--braking movements, perhaps, or pure-carved turns--or adapting movements to different types of terrain or conditions. The same "basic parallel" level student above could go off-piste and explore easy moguls, or a little powder, or maybe something a good bit steeper, rather than just trying to make a "better" parallel turn on the same familiar terrain.
Either option--linear or lateral learning--could be appropriate for any given student, depending on individual goals, desires, needs, and expectations.
The problem with the Center Line Model is that it required the instructor to understand it fully before he/she could apply it effectively. And that seemed to be a lot to ask of most newer instructors. So it was often misunderstood, misinterpreted, and misused--a problem that has been greatly in evidence even here at EpicSki.
So the Stepping Stones concept has come along, to help address the same issues in a simpler way. Like the Center Line Model, it clearly represents that there are different directions for lessons that may be appropriate for different students and different goals. It represents the idea that few students learn best exactly the same way, that students learn at different speeds, that different learning hills have different requirements, and that a single progression of exercises is hardly ideal for all students.
Imagine a shallow, rock-strewn river, with you on one side and your destination/goal on the other. To get there, there are many possible routes across the stepping stones scattered throughout the river. That is the image of the Stepping Stones model. It maps out a variety of routes between "never-ever" and basic parallel turns. There are "direct parallel" paths, as well as paths that explore all sorts and varieties of exercises and tactics. Both linear learning and lateral learning are clearly possible, depending on the student and the situation.
I like the model. I especially like that any instructor could create his/her own "stepping stone" map, creating a "stone" for each exercise or focus in his "bag of tricks." Ski schools can create their own version of the map as well, giving their instructors a variety of options for teaching, tailored to the specific teaching hill and environment and the desires of the management, but also creating limits or boundaries as required. It's a simple idea, flexible, graphic, and customizable. It can change and grow as the instructor's bag of tricks expands.
So the Stepping Stones Model really does replace the Center Line Model in function. I think the Center Line Model is still clearer and provides a better map, once it is understood. The Stepping Stones model, while it allows many possible "paths," does not make it obviously clear where various alternate paths may lead, which the Center Line Model did quite well (once it was understood).
The SS model is new, and time will tell how effective it becomes as a tool in actual use. I have high hopes!