ISI curriculum starts the backspin way later than USFS. It's so crucial for the axel jump, really they should not be introduced in the same level. I'd say probably preceding loop, in FS3? ISI does in fact introduce the backspin in FS3, as part of the change-foot although you can spin on either edge. I will tell you that in competition, many judges will award the higher score to the skater who does a correct outside edge back spin portion, no matter how many times an inside edge goes around. By the way, you need to understand the back spin position not just for axel (FS5) but also for loop and flip (FS4).
Anyway, by way of justification, the "any edge will do" backspin does at least get a skater spinning on the other foot, which is hard all in itself.
Why do they introduce the backspin as part of a change foot spin instead of introducing it as a separate element? Actually, I don't introduce the back spin as part of the change foot, nor do most of the coaches whose teaching approach I'm familiar with. We all do stand-alone back spins. In fact, this is one of the place where Basic Skills shines, with its 2-rotation back spin at Free Skate 2. If this element could be paired at a lower level with the change foot concept, you'd have kids getting easy back spins at FS5.
Here's what Randy Winslip, Director of Skating Programs for ISI told me:
"The back scratch spin in FS5 has always been required to be on the back outside edge - since the requirement for the test portion is to enter from a forward inside edge.I wish someone had told me to start working on my backspin at the same time I started working on forward. I would disagree. Get a solid forward one-foot spin (not necessarily scratch spin) first. Then worry about the back spin. However, it is a good idea to start working on forward scratch spin and beginning back spin around the same time.
While it's great if FS 3 skaters can learn to be on the back outside edge (personally, I always try to teach it like that to save time at higher levels), it has never been a FS3 test or competition requirement for the change-foot spin.The change-foot spin requirement in FS3 is meant to introduce the concept of spinning on both feet - but that concept is not expected to be mastered at that beginner freestyle level. It's more important that the skater can spin at least the minimum required 3 revolutions on the other foot.
Of course, I personally feel the skater will be much better prepared for FS5 and higher levels if the BO edge is emphasized and learned as early as possible."
How quickly should a skater acquire the scratch spin and the back spin? Both of these skills entail what I call "positions not found in nature." They are very difficult. However, spend the time on these and the higher skills-- loops, axel, double, fast back scratch, forward and back sit, will happen quickly. Just as proper stroking and edges are critical for beginner skaters, these beginner free style skills are critical for successful higher level skating. Don't skimp on the lesson time for these because "we have to start working on axels." Work on these skills until they are solid, because in a major way, you are working on axels.
I would not begin to venture a time line. It depends on the skater's talent and motivation, the amount of time on the ice, and the quality of prior skills.
What are your spin questions?