Using ARD to do mass upgrades?
You can use Apple Remote Desktop to copy the macOS Installer application to the Applications folder on every client Mac, then send the following UNIX command as root:

/Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/startosinstall --applicationpath /Applications/Install\ macOS\ High\ Sierra.app --agreetolicense --nointeraction


This command starts the in-place upgrade action to macOS High Sierra. It may take some time for the entire process to complete, but it doesn't require any user interaction.