Does Windows Server 2008 R2 schema require extending for SCCM 2012?

I have a forest that is running a mix of Windows Server 2008 and Windows Server 2008 R2 domain controllers and the schema is at Windows Server 2008 R2 level (version 47).

I am trying to find out if the 2008 R2 AD schema already includes the SCCM 2007 (2012) extensions or not? Given that SCCM 2012 uses the same extensions as SCCM 2007, are the SCCM 2007 extensions already included in the default 2008 R2 (v47) schema? Google search gives me lots of articles on how to do it, but little info on when to do it.

Thanks.