Removing a parent post from a class/community on Bloomz is currently a two step process. The first step is Flagging the post as inappropriate. You can do this by clicking on the arrow located in the top right of the post and hitting the Flag As Inappropriate 

After you flag the post as inappropriate, you will get a notification. You can open the notification by clicking the bell icon located on the top right of your menu bar. After you click on the bell you will see a notification at the top of the screen saying that a post in your class has been flagged. At the bottom of the notification, click Remove Post From Group and it will be removed from your group.