Disabling assignment link after a certain time #42

Hi, I'm new to GitHub Classroom. My understanding of it is that once you create an assignment, you can distribute that common link to all the students and through which they can create their personal repo within the organization by logging into their GitHub account and simultaneously join the organization if they haven't done so.

However, is there anyway we could control who could join the organization or at least disable the link once all the students have joined? One imaginary scenario is that a unwanted outsider somehow obtain the link and join the organization by going through the link. He or she can now see the content of the organization (or at least have the same access privileges as all other default members).

Hope I'm understanding this correctly. Thanks!