why doesn't my callback update my listview?

gistfile1.txt

the function MedicalLst() works If i use it to build student_list.

furthermore, the callback prints the correct list to the terminal.

the question is why won't the callback update the listview?

here is the binding: btn1.bind(on_release= (callback2))

here is the callback:

def callback2(*args):
    student_list.studentAdapter= ListAdapter(data=MedicalList(),
    allow_empty_selection= True, cls= ListItemButton)
    l= MedicalList()
    print str(l)

the print statement returns a proper list to the terminal.

this is the adapter:

studentAdapter= ListAdapter(data=StudentList(),args_converter= list_item_args_converter,
    allow_empty_selection= True, cls= ListItemButton)