In education you will likely exchange files frequently. So having a word processor that can write files that others can read is very important.
So don't minimise the conversion issue, and make sure whatever you choose will be readable by everyone. If you opt for freeware, you are - somehow - morally responsible for conversion when sending a file to someone that uses *paid* software.
Conversion is an art with many surprises that takes time to resolve - and time is money. So freeware is not really free.
Both iWork and the MS-Suite for mac are good products. I would recommend MS because Excel has more powerful functions such as pivot tables.
For ultra basic text editing, don't forget that TextEdit can read and write files in word format (no pictures though).
I've been using OpenOffice and NeoOffice for years now, and OpenOffice 2.3 is a big improvement. I also work in education and for the most part, unless the file has some special function that is proprietary to that suite, the conversion has been pretty good. The conversion excuse given by critics of free and open source apps is a weak one because then the same issue would come up with pay applications like iWork '08 and other commercial non-MS suites (you still have to convert the file
even though you paid for the non-MS suite). And of course, this only happens when you're dealing with such a closed file-format like those of the MS Office suites (which I believe is the only way MS were able to obtain and maintain such a large user base on Office).
BTW, the issue is the same for older MS Office users and MS Office 2007 users since Office 20o7 on Windows uses .docx as the default. So now even if you are using a Microsoft product, you STILL have to deal with the issue of conversion!
On the flip side, most applications now are supporting OpenDocument formats and can interoperate easily with one another, not locking you to one office suite vendor. And with the recent rejection of Microsoft's OOXML format (which really isn't that open), things might look even brighter for interoperability. Remember, no one thought that WordPerfect would lose its grip on the world, and up came MS Office. The same could happen to Microsoft given the time.
And from what I've heard from people on here, the Office suite for the Mac is horrendous to use. Probably not as unMaclike as OpenOffice currently is under X11, but that advantage won't last too long once they release the native OS X version.
To answer BioCore question (albeit a bit late), it should be possible to do this in OpenOffice/NeoOffice, since it's really a matter of how you're going to print out the slides and not necessarily affecting the design of the presentation.