With Parent-Teacher-Conferences looming, a little birdy at Syringa Middle School gave me the heads up (thanks, Haley!) on a Google Forms add-on called "Choice Eliminator" that allows you to design a Google Form that gets rid of choices from the Form as they get selected.  You can control how many times each option can get selected before it disappears from the Form.  This would be a great way to schedule PTC appointment slots or design Forms to have students choose teams or groups for a class activity.