Explain bad grades or hope they won't notice?

Peter Van Buskirk addresses some points relevant to kids I know, in a Q&A with U.S. News & World Report. Van Buskirk is a college admissions officer turned author/lecturer who spoke at my son's school, SOTA, last year. I blogged about his talk at the time.

Some excerpts from the U.S. News interview:

If students get a bad grade, or a bad test score, or some other problem, should they explain it in their application essay?
You don't want the admissions officer to just guess about what was behind a poor grade, because we tend to be cynical and think that the student was lazy or disinterested, not that something horrible happened in your life. This [grade or test score] is something that can be addressed in an interview as well as a note that is attached to your application. In addition, you need to make sure the teachers and counselors who write on your behalf are prepared to speak to these circumstances as well. As you tell your story, though, make sure you provide explanations and insight, not excuses.

You talk about résumé-building and how you can tell if it is phony. What extracurricular activities should students be involved in?
Kids need to follow their passions. I worry that there are a lot of young people right now who are being remade into the images of what somebody thinks a dean of admission wants to see, at the expense of lives well lived. The reality is that deans of admission are constantly looking for that something different in a young person that is genuine.

How can they tell if it is genuine?
Admission officers look to see if you have been involved with a particular activity over time, and if you've grown with that activity. If you've been in the choir for three or four years, well, clearly you like to sing if you've become a soloist , if you've become section leader, if you've become a student director, if you've become an officer in the choir, that suggests you are invested at another level.