Set default desktop for all users

Would you someone please explain how to set all user's desktop to a certain desktop (lets say gnome-classic).

I have tried inputting the desired destkop under each users file in:
"/var/lib/AccountsService/users/

I have gnome-session-xsession package installed and fill out the users file per "https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/desktop_migration_and_administration_guide/user-sessions#configuring-user-default-session".

Every time the user logs in it always goes to gnome3 (we want gnome classic).

Would anyone be able to help me out, thanks!