We have found that Schoology's import and export of quiz questions and answers is broken when the text type is "text/html".
If you build a quiz question or answer of type "text/html" with content like "<this should be surrounded by angle brackets>" in the cartridge, that content will not be imported correctly (everything between the angle brackets, including the brackets) is discarded on import.
Similarly, you can build a quiz question with the content "<hello>" entirely within Schoology, export that to a common cartridge, and then import that cartridge right back as a resource...and the resulting question text is also broken (does not contain "<hello>").
For standards reference on how text/html content should be encoded and handled, please see http://www.imsglobal.org/cc/ccv1p2/imscc_profilev1p2-Implementation.html#toc-67.
This is a fatal error that is blocking successfully roll-out of courses on Schoology customers. I have a test cartridge available for your inspection. Please let us know when we can communicate expectations for a fix to our customers. Thanks!