Every language has a skill tree that maps out your course. You begin learning the basics; as you progress, the skills and levels build on each other and become more complex. As a student successfully progresses through individual skills, they can choose to advance within that skill set to graduate to another level or to select a different skill altogether. Though it was not always the case, students can now practice skills out of order.
Teachers who use Duolingo for Schools are able to assign skills out of order as well. They can also assign XP goals to students to ensure consistent practice. However, Duolingo does not currently track the exact time a student spends practicing. The duration of time it takes a student to complete a skill depends on their understanding and mastery of the vocabulary; though it can be assumed that for many students and language learners, earning 20 XP on Duolingo can equate to approximately 10 minutes of work.
When assigning students to collect points it's possible to choose a short or long assignment. The times associated with completing XP goals below are approximations.
For more information on how educators have used Duolingo for Schools in their classroom, visit the Learning Hub or download a PDF of the Duolingo for Schools: Guide for Leaders in Education.