I have read the documentation on co-teachers at https://support.code.org/hc/en-us/articles/360013399932-Back-to-School-FAQ-Updated-for-2019- which says:
Can I add a co-teacher to my section?
There is currently no way to add a co-teacher to your section. The best solution is to have two teachers create their own sections with the same set of students. If you use Google Classroom or Clever rostering, this can be achieved by syncing to the same Google Classroom or Clever section. Otherwise, a teacher can copy over their students to another teacher’s sections through the “Move Students” button.
We are using Google Classroom for student accounts and have issues with trying to do this. If a teacher creates a section and syncs to Google Classroom and then the co-teacher does the same thing, the sections disappear for the first teacher.
Is there anything we can do so both of us can see student progress?