D. Even those who struggle in their lives outside of school have a responsibility to make an effort with their education.
Explanation:
In the given passage, President Obama reiterates the importance of education irrespective of one's personal life. This Back to School speech stresses the need for kids to focus on their academic life no matter what circumstances they face in life.
By stating that <em>"none [of the circumstances of your life] is an excuse for neglecting your homework or having a bad attitude in school"</em>, the President advised the students/listeners that it is important to try to make school work. Thus, the main idea of the excerpt is that everyone has the responsibility to make an effort with their education.
