I think there's a huge volume of things already written out, just in different publications.

It really becomes a matter of what you want your kids to be able to do and how you're going to teach/refine those skills through fundamentals.

I've taught 6-8 and 9-12 and I always wrote out my own exercises. It's just a matter of if you want to have a ton of different scans or something clean, if you like following someone else's method, etc.