is to get as firm a grasp on the issue (is it just calculus? calculus and certain physics topics? what parts of the calculus?) before you sit down with the tutor so you don't waste the kids time (and your $).
It is very common for calculus to be the first giant struggle for very strong math students. Some of my kids have never gotten less than an A in math, so they don't know what to do when the usual approach only gets them a C level understanding.