user: Question: What is the average roll for Fairfield School?
Columns: ['Name', 'Years', 'Gender', 'Area', 'Authority', 'Decile', 'Roll']
Types: ['text', 'text', 'text', 'text', 'text', 'real', 'real']
Sample row: ['Abbotsford School', '1–8', 'Coed', 'Green Island', 'State', 7.0, 278.0]
SQL:

assistant: SELECT AVG("Roll") FROM "Table" WHERE "Name" = 'Fairfield School';