I teach high school math and science, mostly to students who have not done well in math earlier in their education. So I spend a lot of time doing pre-algebra and algebra 1 work. I love teaching at a school that lets students spend as long as they need on these topics until they truly understand them and can use them in real-world projects. There's no effort to rush students into algebra 2, although I can support students all the way through calculus if it's appropriate for them.
Students do a separate, adaptive curriculum for their skills work. For modeling, they do a series of mini-projects that build their skills. They sketch a number of things like snowmen, robots, apartment buildings, skateboards, ice cream cones - things that can be represented through cubes, spheres, cylinders, and cones. Then they model these shapes and learn to translate and rotate elements. They also learn to use the difference function. The last required skill is using parameters, which is the core of the reason we can offer this for math credit. It makes them think about the relationships between all the parts in their model.
They also have the option of using modules, hull, minkowski, rotate_extrude, or any other feature that helps in their projects. They propose a final project of appropriate complexity. The range of projects is just fascinating.
We may open a Shapeways shop for our school in the next few months. I have two students designing a chess set as an extension project, and one student who came up with a functional design that hasn't really been done well on Shapeways.
I'm happy to share more if you're curious, my email is in my profile. Also, I wrote a student-friendly intro to openscad a few years back:
https://peak5390.wordpress.com/2013/01/08/an-introduction-to...