In "Maniac Magee", why did McNab's group stop at Hector Street?

Hector Street is the racial divide in the town, where the neighborhood on one side is inhabited by white people and the neighborhood on the other side is inhabited by black people. Maniac Magee is the only child who crosses these invisible barriers-- he is not deterred by race. However, the McNabs have been brought up in a racist environment and see the blacks as enemies, even playing games in which they build forts and battle the black people. Therefor, when they reach Hector Street, they do not cross it, despite all their bravado. Hector Street is important in the novel as this invisible racial divide, even Amanda Beale knows she's not supposed to go over to the white side. However Maniac crosses those lines, and eventually brings the two sides together. His actions teach the lesson that people, regardless of race, are more alike than people think. At the core of every human there is love and good.