How to revert a SharePoint 2010 Site Collection to a Default site template from a Custom Template

I have multiple SharePoint site collections that are created with a custom template that I now want to revert them back to a SharePoint OTB default site template (ex. TeamSite "STS#0"). Is there anyway to accomplish this using PowerShell? Can you default back to a default template from a custom template? I rather accomplish this for every site collection using the custom template at once rather than individually running a script for each site that has the custom template deployed.

I want to migrate the sites to SharePoint 2013 but don't want to bring over the custom templates because the features are already in 2013 templates.