Feng Jiao headed to the agency after school to make sure that she handed her report card to Kong Xiulan.
Kong Xiulan had told Feng Jiao that she was allowed to do whatever she liked, as long as her grades remained at a passable level. That passable level meant that Feng Jiao had to come and report her grades to Kong Xiulan every single day.
Kong Xiulan looked forward to seeing her marks, and had teacher Wu tell her whenever there was a test.
There was no other way to make sure that Feng Jiao was reporting back to her honestly other than that. She needed to make sure that Feng Jiao was indeed telling her everything, and that she wasn't hiding anything.
Feng Jiao had a habit of hiding things from the people around her, and Kong Xiulan had realized this when Feng Jiao moved out. When she was living at the agency, Kong Xiulan would find things out from simply looking at her and seeing what she was doing.