In most places the host teacher is providing a service and he or she decides
what lessons will be taught and what the student teacher will teach and when.
After all, your students are your main consideration. Shouldn't your
student's supervisor have worked this out with you?
I have only had a high school teacher cadet in my class (who was helpful and
did well with the lessons she taught) but the supervisor was very good about
explaining the goals and expectations for the placement.