Thats true, however there are many fX.../64 prefixes that are special in IPv6, so these also don't really help with this problem.

@ jcbermu Hey, they also state 'In technical books, articles, and training material, it is often necessary to show examples of IP addresses in use.'. From my point of view "training material" would perfectly fit what we plan to do. Training for me includes practical exercises (or even could be seen synonymous).

Regarding the fc00:/7, see my comment to Sascha R. We internally also had some people argue that the network we use can also be seen as documentation (or at least it is used as practical part of the documentation/explanation of IPv6 to students). Just from the RFC I can't see anything defining that documentation is strictly written text. Do you have any source for this interpretation?

Yes, we also considered the fc00:/7 (or more precise fd:00/8) as option. However, this means that we would need to use 40 randomly created bits + subnet to get a /64 prefix (according to the RFC). Using e.g. 0000... as "random" number would violate the RFC, using real random numbers would render the IPv6 addresses probably very hard to remember for students which is also not desired.