Simply navigate to your class group and click on the box: Share something or ask a question...
2. Write your post in the box, then, click on the button over to the right hand corner as shown below.
3. The icon will turn blue when on. Then, click on the +Add... button.
4. A pop-up window with your other class groups will appear. You can go ahead and select which other class groups you want to send the post to. Then, click Select.
5. You will then see the other class groups as shown. Simply click the Share button. The post is now shared to your other class groups.
See it in action