One day , Zhou surprise the children with a written exam and leave the classroom to speak with a visitor . Wang 's son , Wang Gui ( 王贵 ) , trick their maid 's son , Yue Fei , into completing their assignment while they go outside to play . After easily finishing the task at hand , Yue write a heroic poem on a whitewashed wall and sign it with his name . The children then burst into the classroom upon learning of Zhou 's forthcoming return and tell Yue to escape in order to avoid apprehension . The old teacher eventually discover the ruse and , after marveling at Yue 's impromptu ballad , ask Yue to fetch his mother , Lady Yao ( 姚夫人 ) , for an important meeting . With the entire Wang household assembled in the main hall , Zhou ask the Lady for her blessing to have the boy as his adopted son and student . She consent and Yue take his seat amongst Zhou 's students the following morning . Because Zhou know Yue is poor , he command the four students to become sworn brothers . Zhou also begin to teach Yue all of the eighteen weapons of war .