Sharepoint 2013 Experience all that SharePoint 15 has to offer

Self-service upgrades on SharePoint Foundation 2013 from SharePoint 2010 experience mode to 2013 experience mode are disallowed. 

To disallow, perform the following steps in the SharePoint 2013 Management command-line shell:

$spSite = SpSite("http://www.contoso.com");

$spSite.AllowSelfServiceUpgrade = $false

Introduction to Upgrade in SharePoint Server 2013

http://blogs.technet.com/b/wbaer/archive/2012/07/17/introduction-to-upgrade-in-sharepoint-server-2013.aspx