How to bind collection of collection to a datagrid in Silverlight 4

Question

I have a collection of Departments, which has collection of Teachers and which has collection of all the classes they teach. I was able to create a collection of collection of collection from the data source. Now I want to bind the data to datagrid. What I want to bind is the classes taught in the school group by teachers by department. What is the best way to do this and any pointers would be great. Thanks.,