SELECT MIN("Roll") FROM table_67633 WHERE "Decile" > '6' AND "Name" = 'broomfield school'
What is the smallest roll with a Decile larger than 6, and a Name of broomfield school?
CREATE TABLE table_67633 (
    "Name" text,
    "Years" text,
    "Gender" text,
    "Area" text,
    "Authority" text,
    "Decile" real,
    "Roll" real
)