As the Administrator, you can save the template in your son's user templates folder (the path is usually C:\Users\<user_name_here>\AppData\Roaming\Microsof t\Templates\ but the File Locations dialog box of your son's installation will tell for sure). I believe you also need to give him read & execute access to the file.

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Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional