The key "College" is an array, your trying to treat it as a "subdocument" (but that wouldnt allow for multiple colleges to be stored)
You want the elemMatch keyword here I believe: http://docs.mongodb.org/manual/reference/operator/query/elemMatch/
EDIT: After looking at this again, I think you have your structure a little out of whack. How many "students" will there be per college or school? Keep in mind each parent document can not exceed 10mb, and when you select a document, the entire document must be sent back across the connection (unless you are using aggregate or map/reduce. I would think you may want to have a collection of Persons and then a key associating a person to... something else.