Modifying your templates is how you change your standard.
If they're reverting to iso then you should probably look at your settings in Options because SolidWorks is not using your new templates. Specifically you want to look at:
Options: System Options: Default Templates
and Options: System Options: File Locations and select "Document templates" from the list of search paths
The final factor may be that when you save your templates, you're saving them as regular SolidWorks files (sldprt, sldasm and slddrw) instead of document templates (prtdot, asmdot, drwdot). This frequently happens if your game plan is to modify a template by creating a new document, changing it and saving it to the template file location. What happens, is people forget to change the file type in the Save As dialog box.
Check out those configuration settings and you should be able to get on top of your situation.
I was saving the sheet format so saving it as a template worked.
When I look at the "System options: file locations" I get this - C:\ProgramData\SolidWorks\SolidWorks 2012\templates\
If I try to change it I get this - C:\Program Files\SolidWorks\lang\english\Tutorial\