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Students joined my class and their progressed was erased

I recently created a classroom on Duolingo and one of my students who had already been studying with Duolingo and made significant progress, but when she joined my class, it seems like she was back to square one? She still has her XP but all her lessons went back to 0 crowns. She's a very advanced student and was frustrated that she now has to redo lessons about colors and other really basic stuff. Is there a way to undo this?

June 8, 2020



What course?

She probably was switched back to a previous tree version because of the classroom (stable vs A/B tree tests).


She is an Arabic speaking English learner. I'm not exactly sure what you mean by stable or A/B tree.



No update was posted in the Incubator for the EN<-AR course: https://incubator.duolingo.com/courses/en/ar/status

Quote: I'm not exactly sure what you mean by stable or A/B tree.

A course can have different tree versions.
It gets an increased number when content has been changed, skills added or rearranged.

Progress (skills, lessons) is individually tracked by the system for each tree version.

Duolingo staff constantly runs A/B tests: https://en.wikipedia.org/wiki/A/B_testing

You can see different A/B experiments associated to your account in the extended user profile.

New trees are incrementally rolled out to a subset of new users.
Not everyone gets the new content immediately, especially not old users.

A/B testing is restricted to normal Duolingo accounts (like the latest French from English course with 172 skills).

When a student joins a classroom, A/B testing is stopped and only the "stable" tree is offered to a student.

When an A/B tree test has successfully finished it slowly is rolled out to all users, and usually, but not always, gets a special flag (something like "stable" to my understanding) which also affects classrooms at a given time that this new tree content is finally offered to students/pupils.

This is IMHO the main (theoretical) reason that a tree progress could quickly change, when a new user which has already started a course outside of a classroom, joins your classroom.

Their whole account is marked as a school student hence it is excluded from any A/B testing.

The above explanation seems not to be directly related to the EN<-AR course as this is probably a contributor course or has it been taken over by staff/contractors??

For staff-based courses (French, Spanish, English from ES/PT, Chinese Mandarin,...) new A/B tree versions are not announced on the forum!

Contributor-based courses should get an announcement either on the Incubator or in a forum thread.


I had heard it once that staff had not changed a "stable" flag for a course...can't remember which one.

"Everyone" (=normal DL users) was on the new tree version for a longer time...but not student accounts belonging to a classroom which were fixed to the earlier old tree version.


I'll report this on the Educator's network for you to get more eyes on it.

In the meantime, she can click on one of the castles, which are checkpoints. They will allow her to test out of the earlier levels. She can also click on the key icon on each skill to test out. Yeah, I know it's irritating, but review is good.

Hang tight. I'll report this.

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