Which Year Joined has a Size larger than 93, and a Previous Conference of none (new school), and a Mascot of rebels?
CREATE TABLE "membership" (
  "school" text,
  "location" text,
  "mascot" text,
  "size" real,
  "ihsaa_class" text,
  "county" text,
  "year_joined" real,
  "previous_conference" text
);
SELECT AVG("year_joined") FROM "membership" WHERE "size">93 AND "previous_conference"='none (new school)' AND "mascot"='rebels';