Can a 2009 client access a 2011 PDM server?

I'm in the process of upgrading our university's SolidWorks install from 2009-2010 to 2011-2012.  We have been using the Workgroup PDM 2009, and when I try to log in from the 2011-2012 SolidWorks, it fails, saying that the PDM server needs to be updated.  If I do update the server, will this prevent the remaining 2009-2010 clients from accessing the database?

SolidworksWorkgroup Pdm