People often use 'educational purposes' to mean any copying done by someone who works in an educational institution. This is misleading. It is useful to think about ways in which you can copy copyright material as three increasing levels.
Fair dealing, which allows, among other things, small amounts of copying for criticism and review or for research and private study.
Educational copying, about which more below.
Copying under one of the special licences the University pays for, as do many other educational institutions in New Zealand, that allow you to copy more than the educational provisions do.
In NZ law copying for 'educational purposes' specifically means making copies of copyright material for students in a classroom setting. While you can quote parts of a work in your own published research paper, this is exercising your fair dealing right not copying for educational purposes. And putting a lecture on-line where anyone can access it, such as on iTunesU, is no longer a strictly educational setting in that anyone in the world can access, not just the students in your course. The Copyright Act is very clear that copying under this provision must be for the purpose of instruction and that access must be restricted to people in the relevant class.
For the most part we actually don't copy material under this provision because the licences that the University pays for allow more. However, to outline the educational provision in brief, you can make multiple copies of 3% or 3 pages, whichever is greater, of certain types of work under certain circumstances. You can even make multiple copies of part or the whole of a work by hand. But rather than describe the educational copying provisions (and the important 'certain circumstances') in detail here, they have been incorporated into the table on the page describing what you can copy for students in coursepacks. For more specific information about copying for educational purposes, the New Zealand Copyright Council has produced an excellent, detailed Information Sheet on Education.