How many values for Ofsted occurr at Chowbent Primary School?
CREATE TABLE "list_of_schools_in_atherton" (
  "school" text,
  "locality" text,
  "description" text,
  "ofsted" real,
  "website" text
);
SELECT COUNT("ofsted") FROM "list_of_schools_in_atherton" WHERE "school"='chowbent primary school';