wronged

Yesterday evening I checked my son's homework.
Very untidy handwritten! I advised him that should be clean down.  I tell him to Use the eraser while writing wrong, but he often care it .
I asked him to rewrite on a new notebook but he felt wronged and cried very sadly, I didn't comfort him but continued to cook dinner. He was crying while writing.
When supper was ready ,I checked again. It was perfect this time. I told him "If you're serious of your writing,your writing will treat you well.He looked at what he rewrote and then with a sweet smile.