席順が決まってるって英語でなんて言うの？

• "The seating order is decided"
  "the seating order" 「席順」
  "is decided" 「決まってる」

"The seating order at the cram school I attended in elementary school was decided on grades"
「小学生のとき通ってた塾では、成績に席順が決まってる」

席順 - seating arrangement
決まってる - is decided

"席順が決まってる"
- The seating arrangement has been decided.
- The seating arrangement is decided.

小学生のとき通ってた塾では、生徒の席が、前から成績順に座ることになっていました。
- The cram school I attended in elementary school arranged for the students to sit according to their grades.