The conclusion of the story proves Miss Moore's lesson was worthwhile.  She is getting the kids, in this case, Sylvia to think.  The entire purpose of the lesson was to enable the kids to critically think about their world and their place in it.  Sylvia articulates this at the conclusion of the story.  By breaking off from Sugar and wanting to be alone and needing "to think this day through," Miss Moore's lesson and purpose has been accomplished.  She was able to get the students to think.  This ends up contributing to the story's central meaning in that  there must be some level of critical thought and analysis about the issues that exist in a setting in order to initiate change about them.  Conditions will not change unless individuals are confronted with them and think about them.  This is where the ending, one in which Sylvia must be on her own to think and reflect about "the lesson" helps to feed the fundamental meaning in the story.  Miss Moore did not seek to do anything else but generate thought and reflection in the students.  The conclusion to the story demonstrates this, affirming its central meaning.