512 MB RAM is the maximum RAM of the clamshell iBooks, and 500 MHz+ is required for MS Office 2008.
Tiger can run MS Office 2008, though. Hopefully, I'll get the school to stop using .docx and switch to the Open Document Format... Plenty of students I know can't afford Word.
The TiBook needs to run some bloated web-apps, as well.
My old middle school required office 08' but they then switched back to 04