Over the last few months, we've added new features that improve the groups experience. Some of these include group descriptions, a catch up feature, and protection for people who are being added repeatedly to groups they've left.
Today, we're launching a new group setting where only admins are able to send messages to a group. One way people use groups is to receive important announcements and information, including parents and teachers at schools, community centers, and non-profit organizations. We've introduced this new setting so admins can have better tools for these use cases.
To enable this setting, open “Group Info,” tap Group Settings > Send Messages and select “Only Admins.” This setting is rolling out to all users around the world on the latest supported versions of the app.
SOURCE: WhatsApp Blog