I teach Core French to 6 different classes (4-8). They each have a class set up and students would like to continue their progress next year. I am changing schools. Can I transfer account to the incoming teacher so that the students' data is preserved? It would be a shame if they all had to start again.
That's one of several features that's still missing from Duolingo for Schools. Your students won't have to start again, though. Your successor will need to create a classroom, and then give the classroom code to the students, who will then be able to join their existing accounts to the new teacher's classroom.
It's a very bad idea to join someone's classroom unless they're already your teacher. The Duolingo for Schools system lets your teacher set you assignments, but it doesn't give you access to anything on Duolingo that you can't already get at. It isn't like an actual classroom - it isn't a place where someone can teach you.
It also lets your teacher change your Duolingo password, see your email address, and disable your access to the forums and certain parts of certain skills.
Of course! If you show them what their grades are in French 1/2/etc and show them you have the student grades and classes they did, they will likely either start the same level for next year or might be sent back one if they either struggled or the teacher is a faster teacher. I really see no reason why you can't successfully propose this to the school principle.