You now have the ability to upload an assignment in Google Classroom and ‘Save Draft’; and assign when necessary.
Create an assignment as usual, but instead of ‘Assign’ choose ‘Save Draft’. It will then appear on YOUR wall as ‘Draft’. When you are ready to ‘Assign’ either click on ‘Draft’ or the arrow on the right. Then click the name of the assignment, a pop-out window appears where you can see the settings of the assignment and have the option to ‘Assign’ or ‘Save Draft’. This time ‘Assign’.