What is Active Directory Schema?

The schema is the Active Directory component that defines all the objects and attributes that the directory service uses to store data.

Active Directory stores and retrieves information from a wide variety of applications and services. So that it can store and replicate data from a potentially infinite variety of sources, Active Directory standardizes how data is stored in the directory. By standardizing how data is stored, the directory service can retrieve, update, and replicate data while ensuring that the integrity of the data is maintained.

Active Directory Schema Version:-

Version Windows Server Edition
69 Windows Server 2012 R2
56 Windows Server 2012
47 Windows Server 2008 R2
44 Windows Server 2008
31 Windows Server 2003 R2
30 Windows Server 2003
13 Windows 2000

How to find the Schema Version in Active Directory?

Using Power Shell:-

Get-ADObject (Get-ADRootDSE).schemaNamingContext -PropertyobjectVersion

Using Registry (from server 2012 R2)

HKLM\SYSTEM\CurrentControlSet\Services\NTDS\Parameters\<Schema Version>

dsquery:

dsquery * CN=Schema,CN=Configuration,DC=Root-Domain -Scope Base -attr objectVersion

ADSIEdit:

open ADSIEdit and navigate to “CN=Schema,CN=Configuration,DC=domain,DC=local”, right-click “Properties” and locate “objectVersion” attribute value

more detailsPlease refer the below link for

How to find the current Schema Version
http://support.microsoft.com/kb/556086