Hi there! My name is***** am a computer professional with over 15 years of experience with both Mac and Windows computers, phones, tablets, and printers. I know this frustrating for you and I really hate to be the bearer of bad news but there is not currently a driver for the Xerox Workcentre M24 that works correctly with El Capitan. You can view the official document from Xerox with the latest drivers that have been released for El Capitan here http://www.office.xerox.com/latest/SFTDS-02U.pdf.
It would probably be a good idea to check from time to time to see if a driver has been released. Unfortunately, at the moment the only way to get the printer to work properly would be revert to an earlier version of the MAC OSX operating system. If you'd like help with that please let me know and I will be happy to help.
If the information that I have provided has been helpful, would you mind taking a moment to rate my service? I'd really appreciate it! You can give your rating by selecting the stars located on the top right of the question page. As an independent contractor for just answer, I do not receive credit for my answer and I am not compensated in any way without a positive rating. Thank you for your consideration.