I would take the test again and see if you can get a 33+. 31 is a very good score, however the Ivies will turn down plenty of kids with 34-36. You don’t need a perfect score. You need great grades, a very competitive score and the balance of things they want to see in a student (that’s the tricky part- all competitive unhooked kids will have strong LORs, essays, ECs, etc.) Lower scores mean you must compensate in other places - like national award winner in X, solid research exp from prominent organization, etc. Getting a 33+ in no way guarantees you anything, but having less than that puts a lot of stress on the rest of your application.