Sadie's career teaching domestic science is the perfect representation of her approach to life.
Like her father, Sadie is driven by a desire to help her people. A life enslaved does not prepare one for life in American society, and many of these former slaves (and children of former slaves) don't have the tools they need to succeed. Not everyone was as lucky as Henry Delany, who learned to read and write from a young age. But it's not all about literacy: "oftentimes, learning to read and write for the children was not the top priority" (4.13.13).
Sadie wants to give the people who "weren't raised properly themselves" the tools they need to live good lives, and a good life usually starts in the home (5.22.5). It's not the flashiest way to make a difference, and it certainly won't get you on the cover of Time Magazine, but Sadie isn't interested in that. She's interested in helping her generation—and the generations that follow—attain better lives for themselves.