This is a common problem when going from Windows to Mac OS 9. It is not an issue with OS X. It's been a long time since I've worked in OS 9, but if I recall correctly, there was a system extension you could install that allows OS 9 to read Joliet-formatted CDs (that's usually the default CD burning format on Windows). If that's too hard to track down or if you aren't allowed to install anything on your school's computers, then you might try burning the CD as an ISO 9660 disc.