The technical climax, in my opinion, is when the reader discovers that the Hutchinson family receives the tell-tale black spot. If the rising action focuses on the preparations for and the beginning of the lottery, then the technical climax must be when we discover who wins.
If this is the case, then the dramatic climax occurs when Tessie is the member of the family who draws the black spot again. The tension that the reader experienced throughout the text is finally realized when one knows the exact individual who wins. The reader can assume that the prize is an undesirable one based on the tense behavior of the crowd and Tessie’s immediate protests.
The ultimate resolution occurs with Tessie’s stoning, which includes a chilling description of her youngest son being helped to pick up some stones.