In "Raymond's Run," what poor treatment does Raymond receive because he's special?

In Toni Cade Bambara's "Raymond's Run," Squeaky is largely responsible for taking care of her older brother Raymond. Although Raymond is older and bigger than Squeaky, his mental development does not match his age and physical size. Squeaky never specifies what makes Raymond developmentally behind many of his peers; instead, she merely says he has a "big head" that people sometimes comment on or ask him about.
Squeaky takes running very seriously and competes in a lot of races. To prepare for a race, Squeaky practices her breathing exercises and tries to strengthen her knees while going around her neighborhood. Raymond accompanies Squeaky as she practices her running, which means he must also run with her. Squeaky says Raymond has good motivation to keep up with her: "if he hangs back someone’s liable to walk up to him and get smart, or take his allowance from him, or ask him where he got that great big pumpkin head."