Add a feature that allows Co-Teaching

I really wish we had the ability to add a co-teachers to a classroom.  We use the Khan Mappers in our classroom almost daily.  It would be really nice if other teachers were able to be apart of my classes.  Especially, the teacher I co-teach with.   Not only would be both be able to see the results and progress, but we would both be able to assign material to students and better differentiate when necessary.