Create a special page (either in core or as an extension) which lets you view
the html generated by the wikitext.
- You have a wikitext form, like the action=edit one, and a «Preview» button.
- When you click on that «Preview» button, instead of being shown the
equivalent html rendered, it is shown inside a textarea.

This is bug 56694

Students are required to read Wikimedia's general instructions first.