Your professor will read your paper, and perhaps your paper will be discussed in class, but it will not be shared outside of the classroom. You carefully cite the photographs in your paper, so you know you are not plagiarizing, but are you infringing on copyright? No, this is not considered copyright infringement because the photos will only be shared in your classroom.
I appreciate this distinction. I was an elementary education major for two years and using copyrighted photos for anything meant to be used by instructors in a classroom without permission is copyright infringement, unlike if a student uses it. I sort of forgot that that wasn't the rule for most students.