A tragedy that befalls Vernon and Petunia Dursley a year before their nephew is placed in their care changed their outlook on life, magic and Lily Potter. How different would Harry have been if he had been raised by family that cared and encouraged him instead of hating and putting him down. What would his Hogwarts years be like if he had more knowledge at the very beginning?
A tragedy befalls Petunia and Vernon Dursley early on, leading to a very different upbringing for Harry. Entering Hogwarts with more knowledge makes Harry's Hogwarts years very different, with a different House and a few different close friends. Warning- this is just one scene of a story I'm thinking of writing.