PLEASE NOTE: This feature is currently in Beta release and is only available on limited school accounts for now.
Go to the Tasks tab in your class.
On the task containing the custom quiz, click on the student completion summary.
In the Overview and Marks tabs, you can see who has completed the quiz, how your students have performed, and which questions were the most challenging.
To learn more about using this data in your classroom, check out our guide to informing your teaching with data.