user: Question: What's the best average score with a bad score of 15?
Columns: ['Dance', 'Best dancer(s)', 'Best score', 'Worst dancer(s)', 'Worst score']
Types: ['text', 'text', 'real', 'text', 'real']
Sample row: ['Cha Cha Cha', 'Alesha Dixon', 39.0, 'Gethin Jones/Kenny Logan', 22.0]
SQL:

assistant: SELECT AVG("Best score") FROM "Table" WHERE "Worst score" = 15.0;