Spring-Data mongodb requesting multiple classes stored in the same collection

With Spring-Data, you can use the @Document annotation to indicate which collection to save the object. Say I have two classes: Student and Teacher, both stored in a collection of people. When I execute the following code:

mongo.find(new Query(), Teacher.class);

The result contains both the student and the teacher. In the data created by Spring -Data, each document contains a "_class" field, which indicates which class it is stored from.

Is this a field that is not used in the search as a filter to return only Teachers? How can I request only Teacher, except for this:

mongo.find(new Query().addCriteria(where("_class").is(Teacher.class.getCanonicalName()), Teacher.class);