Weston's remark about Braithwaite in Chapter 2 is about his race. It is meant as something in jest, but it reflects more. Initially, Braithwaite is an outsider to the school community because he is a man of color, but also because he is a young teacher. Weston is a veteran teacher, burned out in his profession and scornful of the children he is consigned to teach. In his comment to Braithwaite, he wishes to make clear that the young teacher "know his place."
Weston's comment is a crude racial joke about "Black magic." The remark highlights everything Braithwaite confronts in his new position. Being a man of color, being a new teacher, and serving in the capacity at this particular school with these particular students are all formidable obstacles that Braithwaite must navigate in order to find success. Weston's remark no more than five minutes at the school helps to highlight exactly what Braithwaite faces. It is a comment that demarcates the line between the young teacher who is not jaded and the veteran teacher whose eyes have been blinded with cynicism.