Filtering through multiple ListView WPF

I'm creating an application that uses WPF, MVVM and using the singleton pattern. I have an issue however when trying to filter through a list.

Here is my scenario of using the singleton pattern and using it within my application. I have a School, and a Course; 

SchoolListViewModel -> SchoolViewModel -> CourseViewModel

The image below show three different section. Section 1 shows a list of Schools that uses a filter. Section 2 is a set of criteria in which I want to filter section 3. 



However, When I apply the following code it some how does not load any course data at all nor does it filter through the list using a name search.

Could anyone enlighten me or point out what I am doing wrong or if I am doing is correct?

Thanks in advance.