Limit to one response per person

I need the form set so each student can only submit once. Lock submissions to one response per person for the Biology 101 quiz due Friday, and check the settings so no duplicates slipped through from last week’s lab survey.

Before I send this to the class, make it obvious to students that only one submission is allowed. Put that rule next to the first question, explain how Google accounts are used to enforce it, and flag any existing responses that look like duplicates from the same email.

Two students from Section A filled the quiz twice; I’m not sure if they used separate accounts or one shared device. I’m worried banning all second submissions will block students who legitimately used a different school account. What’s the most likely cause and the safest next step to enforce one response without unfairly locking anyone out?

Across several course surveys I still get duplicates despite toggling single-response settings. I lose time cleaning and explaining to students. What habitual change should I make to reduce duplicate submissions and the follow-up work? Suggest one setup and one communication habit to fix this long term.