Adult characters are able to look at a situation from an objective standpoint. Teen, tween, and child characters are not as adept at being objective. In fact, a totally objective MC might not be very interesting. The reader wants to know what the MC feels, his motivations, his private thoughts, and how these things are expressed through the MC's actions.
For this prompt, describe a minor traffic accident between a mom driving a minivan and a kid on a bicycle, as seen through the eyes of the MC. The MC may be a bystander or the kid on the bike. Who was most at fault? Would the MC have any moments of objectivity? Write for 10-15 minutes.