Something has changed since last school year. Then it was the rare student who had completed the assignment but DIDN'T have the assignment as "completed" on my class/assignment page. Now, many students are completing the assignment, but it does not get the check mark, even though it may say "3 of 3 completed". What is going on? Does this have to do with the crown system? If my students do the lessons, I want them to get credit for it. Some students are having to do the lessons 3 or 4 times to complete, some are getting it the first time. This is very different from previously.
At the moment, there are several bugs in "Duolingo for schools".
You might have a look at the comments of admin KevinR86 in these discussions
Yesterday I reported to one of the mods, via email with print screen attachments, this situation where a student (who has been in my class since the begingning in February 2020) shows completed the 6 first skills asigned, equal 6 blue checkmarks, and in the activity detail it says course progress 0 zero.