When adding Lesson requirements, you can specify that students must move through Lesson items in order. This option means that students must complete one Lesson item before they can progress to the next item in the Lesson.
Note: You can only allow students to move through a Lesson if you have added Lesson requirements.
Once you have a Course selected in the Courses and Groups dropdown menu, click the Lessons link in the Course Navigation bar.
Hover over the bar of the Lesson and click the Edit link.
Require Sequential Order
Under the Lesson requirements, click the Students must move through requirements in sequential order checkbox.
Click the Save button to confirm your changes.