What's the best average score with a bad score of 15?
CREATE TABLE "highest_and_lowest_scoring_performances" (
  "dance" text,
  "best_dancer_s" text,
  "best_score" real,
  "worst_dancer_s" text,
  "worst_score" real
);
SELECT AVG("best_score") FROM "highest_and_lowest_scoring_performances" WHERE "worst_score"=15;