What is the dance that has priscilla presley is the worst dancer(s), and the worst score of 21?
CREATE TABLE "highest_and_lowest_scoring_performances" (
  "dance" text,
  "best_dancer_s" text,
  "best_score" text,
  "worst_dancer_s" text,
  "worst_score" text
);
SELECT "dance" FROM "highest_and_lowest_scoring_performances" WHERE "worst_dancer_s"='priscilla presley' AND "worst_score"='21';