Here's the current list of Schema Versions for Active Directory on Windows Server.

You can validate the current schema version you have in your environment via PowerShell or Registry Editor.

Validate schema version via PowerShell:

Get-ADObject (Get-ADRootDSE).schemaNamingContext -Property objectVersion

In this screenshot, I have ObjectVersion equal to 69, denoting the schema has been extended for AD on Windows Server 2012 R2.

Validate schema version via Registry Editor:

1. Click Start and search for
2. regedit
   
   
3. Open up regedit and navigate to Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\NTDS\Parameters
   
4. In this screenshot, I have Schema Version equal to 69, denoting the schema has been extended for AD on Windows Server 2012 R2.