The easiest thing to do is make a copy of the form and import it as a new form. You can then rename and unpublish the old one so that you have access to the old response data. If this sounds acceptable, do the following
  1. Create the copy by opening the form in edit mode, clicking on the arrow attached to the Save Form button and choosing Export Form. A popup appears to confirm the version of Ecollect necessary for this form to work properly. Dismiss it and a download begins. 
  2. Return to the form list and click New Form. Choose Import and then select the file you downloaded. A new copy of your form appears that you can rename if you wish, and save. You should double check the school share permissions, sometimes they are lost when importing a form. Now you have the same form with no responses. 
  3. You can now unpublish the old form and rename it to differentiate it from the new one (ex. Demographics Form 15-16).