Article version: GitHub.com
Restricting repository visibility changes in your organization
To protect your organization's data, you can configure permissions for changing repository visibility in your organization.
You can restrict the ability to change repository visibility to organization owners only, or allow members with admin privileges for a repository to also change visibility from private to public or public to private.
If an organization owner has restricted repository creation to organization owners only, then members will not be able to change repository visibility. If an organization owner has restricted member repository creation to private repositories only, then members will only be able to change repositories from public to private. For more information, see "Restricting repository creation in your organization."
In the top right corner of GitHub, click your profile photo, then click Your profile.
On the left side of your profile page, under "Organizations", click the icon for your organization.
Under your organization name, click Settings.
In the left sidebar, click Member privileges.
Under "Repository visibility change", deselect Allow members to change repository visibilities for this organization.