Translation:The school's principal is on the second floor.
even just "principal" should be accepted. It's rarely used as a title outside of schools and maybe government..and if you are talking to someone who is already at the school and being directed to the second floor..context would seem to be enough to make it pretty clear that you are telling them that the school's principal and not the Secretary of Defense is up on the second floor....
" the director of the school is on the second floor " was marked wrong. Is it that literal? So depending on context director can mean headmaster, principal or CEO?
it is probably just how the people at duolingo interpret the russian phrase into American english. we would never call the principal of a school a director. Although I think the literal translation should be accepted considering we are trying to learn russian and not english in this course. lolz.