But as you learn where the minefields are in the previous try, your future designs are likely to be better. If you stick to a relatively well-defined standard language, your first designs might be somewhat broken. I believe that designs (and learning how to design) are iterative processes. I have yet to meet someone who really understands UML. A subset of these are likely to be used in any large object design, so why not use UML? (Devil's advocate: one could also argue that it's waaay to many diagrams). UML offers a large number of views, each with their own purpose. What the student should be able to take out of the course is the ability to apply modeling techniques to any system, regardless of the representation. They could roll their own modeling language, pick a random one from a barrel or a pick something that is a bit of a standard and has some industry acceptance. Professors need some model to teach in software engineering, software process and modeling courses. I don't know if this is the answer that you're looking for, but here's an idea.

At the risk of sounding like a PHB, one of its goals is to provide a standard way to show your system's behavior and structure (in particular, from a fairly high level of abstraction).

Dia uml tool recovery