After Students have been mass-onboarded via CSV, they must join their teacher's groups so that they can work with their teachers. 

First, teachers should distribute the invitation code of the group they wish students to join. This can be found on the My School page under Groups.

Second, students should enter this code on their own groups pages. Go to the upper right menu and select the Groups link. On the groups page enter the code in the field on the right, and click Join.