My family got by for a long time on a legal XP + MS Works. They then had to pirate the real MS Office because teachers at school only accept PPT files, and OpenOffice's export was too broken.
I buy all my software but I still can't really blame them.
Office 2010 Home And Student is $119 and it gets you Powerpoint, Word, Excel, and OneNote.
If that's too much, though, I'd recommend just using either http://office.live.com or http://docs.google.com. They're easier to use, the files don't get lost, they have all the features students will need, the documents auto-save, they're available on any computer with an internet connection, it's easy to share the documents (read-only or read-write) online, and the services are free. I've set my daughter up to write all her papers online, and it works great.
If you haven't tried http://office.live.com, you should check it out. It's really a slick.
I believe in copyright and commercial software and everything, but teachers should not press my family into buying software when free alternatives exist. They can just accept PDF slides which OOo can produce, since when are slide animations critical?
I think the "more right" reaction would be to complain about this, at increasing levels of hierarchy, rather than support a monopoly that will push the $119 bill on other families who might be worse off. Either way, I don't blame them for not wasting too much time on it.
I buy all my software but I still can't really blame them.