Assign to Multiple Classes
When creating a Google Classroom assignment you can assign to multiple classes. In the upper left where it says “For” notice the tiny triangle next to the class title. Click on this to select multiple classes to assign the assignment to.
Individual Students Disabled
When creating an assignment for an individual class you can assign to only certain students in the class. When multiple classes are selected, individual student selection is disabled.
Scheduling is Disabled
You can not schedule an assignment to multiple classes. You can save it as a draft, but not schedule. Set a calendar reminder to post the assignment at the desired scheduled time.