The duck is the child who does well in math and poorly in English and is given tutorials by the English teacher while his classmates are doing math. He loses his edge in math, and only does passably well in English.
鸭子是那些数学学的好但是英语不及格的孩子，在平时其他孩子在学数学的时候，他却被英语老师叫去补习英语。最终，他的英语基本达到了及格，与此同时，他在数学上的优势也已经荡然无存。