Sharing between OU and Google group in same domain

Hello.... I am trying to setup sharing between a specific OU and a Google group, both are in the same domain. This is for students at a detention home and their respective teachers. The only items they should be able to share are homework assignments with the teachers. I do not want any other sharing to occur except between these to entities. I've already gone into Apps > Google Workspace > Drive and Docs and shut off all external sharing to the outside for both the students OU also the teachers Google Group. I have turned off external Chat, and I've gone into GMail and set the restricted delivery to use a teachers address list only so they can only send and receive emails from approved teachers. Are there any other settings I am missing? I am not able to find anything about restircting internal sharing. Thanks for any help offered and I appreciate your time.