Several comments say children of younger ages write their own epitaph at school and it's a good exercise. Others complain about the child's failure to communicate with the parent. Others tut at the letter writer's poor standard of spelling and punctuation, some blaming the school, others blaming the parent.
1 Psychology
Teachers are sent on annual courses to update and refresh skills. I would expect them to be taught basic psychology about positive thinking. Even a Shakespeare play has a prologue and epilogue so the audience are brought back from identifying with the characters' emotions to taking an independent unemotional view. Given the number of teenage suicides, in some areas several, at least one suicide the week the report of this dying child incident happened (June 2012), I would expect steps to be taken to maintain morale.
The piece of work should be framed by an introductory sentence or paragraph, and end with a conclusion, stating that it was an exercise and how the writer felt and expects the reader to feel eg that he realised he is lucky to be alive and wants his parents to know he loves them.
2 Communication
The event is a classic example of miscommunication when one person assumes the listener or recipient of information knows the background story. Here person A (in this case the child) assumes that person B (in this case the mother) knows what was said by person C (the teacher). You remember the background to the story but not the people involved at the time.
3 Layout
Teaching layout and tidiness as well as punctuation, grammar and spelling is easier if you start when the child first learns or at least is primary school and do not have to try to change and improve a 14-16 year old. I've been home tutor to 14 year olds and if they are motivated and bright they can learn to get it right by the time they are 16 and take O level. But I've seen precocious oriental children turn it projects with each page framed with a faint pencil line and the whole project tied with ribbon through two punched holes on the left. I try to teach every child of every age to sit straight in their chair, and have their paper horizontal. I show them how to draw a pencil margin, or a frame around a blank page (also out of self-interest so I can correct spelling mistakes in the margins and add a title at the top and comments and praise at the end). If I'm short of time I'll do it myself and eventually they learn to copy me.
On a blank page (or when addressing an envelope) you can draw a faint pencil line for each line of text. or simply divide the page into four even spaces for paragraphs. (without a ruler you can fold the paper).
For headings or important titles, then use a ruler to keep your writing above the line. If you write directly against the ruler and are using lower case, and add the lower parts of letters such as g afterwards.
Summary
For teachers and parents:
1 Ensure each piece of work is positive or framed with positive comments.
2 Communicate with the reader or listener.
3 Pay attention to layout, punctuation and spelling from the start of the pupil's learning process