You will of course need to expand the brief analysis of the theme of these two fascinating stories by unpacking the style of the author in conveying the message.
"The Rocking Horse Winner" is clearly a fable about greed and in particular its dangers. The mother in the tale is consumed by greed, to the point where it alienates her from her children and her son is driven to desperate lengths to help his mother. It is important to note that even the temporary relief provided by Paul's "winnings" only serves to augment the sense of greed and the voices in the house that drives the children wild. In the end, in this didactic short story, D. H. Lawrence shows us the danger of greed by allowing the mother to gain the wealth she desires, but only at the expense of the death of her son.
In "The Lottery", one of the central themes of the story is the violence and cruelty inherent in even the most civilised of societies. A big part of the message of this story is conveyed by the twist of the tale only revealed at the end - we never find out the "prize" of the lottery until the very end, where the chilling significance of the piles of stones made by children at the beginning is brought home. Even the most advanced societies are able to commit and perpetrate hideous acts against one of their own, even an innocent member, and linked to this is the inability of the group depicted in the story to stand up as individuals and protest against the violence. In the end, all participate in the grim act of violence that brings the tale to its close.