It's been probably twenty years since I read
Matilda so I don't remember much of it.
It might be interesting to get the story from
Agatha's point of view, but really, the whole "unwanted child conceived unwillingly, despised by everybody and bullied by the other kids who grows up to be a bully herself" business is trite and predictable. I'd rather see
Agatha herself tell the story and show how she maybe started out to be a decent and good person, but became disillusioned because of some of the spoiled, bratty and manipulative children in her school. Maybe she tried to help one and the kid didn't apprciate it or became greedy and tried to ruin her out of spite, and the whole thing soured her on children and teaching in general.