Rather speak to the school about using Office 2007 or newer and buy the home & student edition. I did my ICDL on Office 2007 but did some online tests with Office 2003, no difference with the end result - its just the ribbon device that separates the two at this level.
Also ask if you could use OpenOffice/LibreOffice 3.0 - its perhaps more similar to 2003 than M$ Office 2007+