How many class AA in the year 2002-03
CREATE TABLE "list_of_prior_winners" (
  "school_year" text,
  "class_a" text,
  "class_aa" text,
  "class_aaa" text,
  "class_aaaa" text,
  "class_aaaaa" text
);
SELECT COUNT("class_aa") FROM "list_of_prior_winners" WHERE "school_year"='2002-03';