Andrew Carmichael is the youngest casualty of the battle. They find his body pinned under an older Ravenclaw girl that had tried to protect him. Tried and failed.
No one can quite figure out how he managed to stay behind. He couldn't have lied about his age. He's too small for anyone to even entertain the notion that he might be of age. He couldn't have given the prefects the slip on the way to the Room of Requirement. At least three people claim to have seen him get into the portrait hole that lead to the Hog's Head.
In the end it doesn't matter. Andrew Carmichael is dead, and knowing how he managed to get himself that way isn't going to change that.
It falls on Minerva McGonagall to tell his parents. She arrives at the Carmichael mansion at eleven thirty the next morning and tries to ignore the unpleasant twisting in her stomach. She is let in through the front door by a house elf stands in the great room next to a picture of Andrew and waits.
His mother collapses as soon as she sees Minerva. His father just stands there nodding stiffly as Minerva relays her message. She can't look at the sobbing woman on the floor; she can barely meet the eyes of the pale, drawn man before her. She leaves after twenty minutes, brushing aside Mr. Carmichaels thanks and apperating back to the school.
Years later she is asked what she remembers most about the battle. She tells them Andrew Carmichael's death.