Reliable, freely available data is an important building block for the workings of a modern society. One of the Appleseed goals is to Educate about Open Data, with its advantages and limitations.
A common factor of these sources is their transparency, Open contributions, open history, contribution rules and culture.
Wikipedia
There is much more to Wikipedia than the page about a subject. Every page has a ‘History’, which preserves all the changes which have been made to that page.
It is possible (and fairly easy with access to a Linux server), to run a local copy of Mediawiki (the underlying software). Schools could run their own copy, to allow pupils to experiment with creating pages, updating other peoples pages, reverting vandalism etc.
Openstreetmap
GIT
Most Free Software projects now run in a GIT repository, which is a way of making their source code available,
People considering a career in IT can create an account in one, or more of the large git repositories, and contribute to projects. Their contributions are then visible to potential employers.