The schema version is revealed via the objectversion attribute off of the schema object from your configuration head of the forest i.e “cn=schema,cn=configuration,dc=yourdomain,dc=int”.

So using Quest Cmdlets, you can run this query :

Get-QADObject "cn=schema,cn=configuration,dc=yourdomain,dc=int" -ip objectversion | select objectversion

The –ip is the alias for includedproperties.

And, when using the native AD Cmdlets of Server 2008 R2 (ADWS), the syntax is slightly different ;

Get-ADObject "cn=schema,cn=configuration,dc=r2,dc=lab" -properties objectversion

Above, you see the query ran with Quest Cmdlets resulting in objectversion 31 which is against a Server 2003 R2 Forest, whereas the latter is for a Server 2008 R2 Forest i.e Schema version 47.