What is the greatest point of an Entrant of connaught engineering alta straight-4 engine before 1957
CREATE TABLE "complete_world_championship_formula_one_" (
  "year" real,
  "entrant" text,
  "chassis" text,
  "engine" text,
  "points" real
);
SELECT MAX("points") FROM "complete_world_championship_formula_one_" WHERE "engine"='alta straight-4' AND "entrant"='connaught engineering' AND "year"<1957;