what AAAAA class has the school year of 1990-91?
CREATE TABLE "individual_overall" (
  "school_year" text,
  "class_a" text,
  "class_aa" text,
  "class_aaa" text,
  "class_aaaa" text,
  "class_aaaaa" text
);
SELECT "class_aaaaa" FROM "individual_overall" WHERE "school_year"='1990-91';