With the introduction of Office 2007 for Windows and Office 2008 for Mac Microsoft changed the default file format documents are saved as. Most of our computers use Office 2003/2004 and as a result you may not be able to read a document you created at home using Office 2007/2008 in school unless you save it in the older format. Fortunately it's an easy thing to do.
Notice that the new format puts an "x" at the end of the document extension. That's the problem.
When you create your document and save it (file - save as), click the "format" pop-up and choose "Word 97-2004 Document (.doc)" then save. Follow the same procedure for PowerPoint or Excel documents.
What if you forget and bring in a document saved in the new format? We do have some computers with file converters installed. A computer teacher/technician can help you.