If you want to automate disabling the App Store auto check, the terminal equivalent of System Preferences > App Store > Automatically check for updates is
sudo defaults write /Library/Preferences/com.apple.SoftwareUpdate.plist AutomaticCheckEnabled -bool false
This is handy to know in case you’re managing updates a different way (e.g., Munki) and don’t want your users pestered with update messages directly from Apple.