After you've added a User, you can assign them to their Class as a Teacher. This solution will also work if users / teachers say they have a blank screen when they log in at

1. Go to "Edit My School"

2.  Go to the "Classes" tab

3.  Click on the name of a class and when it drops down, click "Edit Class Info". 

4. When that comes up, there is a "Teacher" dropdown. Select the corresponding User/Teacher for that class. 

Then, when that user logs in, they will be able to view the class that they are assigned to.