Ironically, Miss Moore is not a certified teacher, but a woman who feels that educating the neighborhood children is her drive and goal. She finds little resistance from the parents, who are more than happy to have their children out of the house. She packs them off to FAO Schwartz so that they can look at toys with prices they could never afford. In the process, she hopes they will learn that differenced do exist between the classes and that money will get the children more in life. Ultimately, the lesson is that no, life isn't fair, but that it is better if you are wealthy.
It is hard to answer this question because the narrator, Sylvia, is so opposed to the lesson herself. As an intelligent and street-wise girl, Sylvia has always understood the subject of the lesson, but balks at admitting it. Admitting her understanding would, according to Sylvia, indicate weakness. In addition, she becomes annoyed when her friends begin to "succumb" to the lesson.
Miss Moore is not teaching arithmatic or diagramming sentences. She is, in fact, teaching life lessons. These lessons are vital, so yes, she did make the right decision.