Hello Erin! My name is Lisa Krueger and I am a Khan Academy Ambassador teaching in Chicago. Unfortunately, there is no way to stop students from removing a coach. Last year I had a few students who did this because they thought if they deleted me I wouldn't know, but of course when I started giving incentive prizes for minutes, videos, and skills they said they 'accidentally' deleted me and needed to re-add me. Hopefully this helps. Thanks for posting. 

Is Khan Academy looking into any way of making students require teachers to confirm removal. Instead of just letting students remove themselves and then taking time away from instruction to make students re-add themselves back into the class. If a student requests removal that request is sent to the teacher to confirm/deny? I had a student remove themselves while in quarantine and then they didn't respond to emails to rejoin my class, so when they returned from quarantine they had missed weeks of content that was assigned and not surprisingly they did not catch up very well. 

I know that if the student has a parent attached to their account then it can be harder to remove teachers if the parent has a certain setting turned on, but I also know how hard it is to contact and connect with some parents/guardians.