Tony was filling out a large quantity of paperwork. It wasn't technically what he should be doing during his office hours, but there was a lot to do in the managing of a business, and allowing his son access to Stark money without raising eyebrows was part of the reason he had so much to do. He didn't want people to know yet that he had a son, as that would draw a great deal of attention to the boy, who was trying to get through his NEWT year. That alone was a lot of work and Tony didn't want to make that harder on him.
When Wan entered he shuffled some of the papers, setting them back into the drawer that held the majority of his files. He wasn't quite sure why a fifth year- even one that was of age - was applying for this position when he had to know that there were a number of more qualified and interested people in the school. It was his opening gambit, after looking at the boy for a few moments. "Why would you want this job?" Because this was Stark Industries. Only the best and most dedicated could even be considered.