In the scene where in Francesca imagines that she was Trinity
from The Matrix, the reflection of the door knob shows that she was still wearing her old clothes from the previous scene and the not the tight leather clothing of Trinity. In the next shot she slowly raises her hands to her head, but the next shot shows her hands are already on her head, the follow shot shows again her hand being slowly raised.
In the basketball scene where Francesca is being recruited, when the crowd jumps up to shout, you can see that Kyle, Matty, and Francesca are already out of the scene yet they walk off the bleachers in the next cut.
In the ETS building, just after they discover they can't print the exam document without three more passwords, there is a face visible through the glass at the lower right of the screen as Francesca is saying "Yeah, we just need the answers."
ETS regulations require that math problems' answer options must go in numerical order. When the six are looking at the test on the computer, the second question goes A: 5 B: 3 C: 9 D:8 E:6. Obviously, these are not in numerical order.
The cheat sheets the kids made only had the letter answers. The SAT uses many different forms with both a different order of questions and a different order of answers. So the cheat sheets would have been useless.
At one point, Desmond says that he could "Ace the math and still not get a 900." You get 400 points simply for putting your name on the test, 200 for verbal and 200 for math, leaving 600 for either section. If he were to ace the math section, this would leave him with a score of 1000 points, which is higher than a 900.
In the ETS building, Francesca and Matty are supposed to be on guard while the other four students take the test. Previously, they needed to sneak across the floor to avoid the security camera, but now they are sitting on the desk in plain view of the camera.
The premise of the movie, that the SAT test has an answer key that is written down somewhere and can be memorized or taken, is false. In reality, each test was distinct and unique, to prevent such cracking of the code and cheating of the systems. There is not a way to control which student receives which version of the test, in order to prepare fully a reliable list of answer codes for any student or group of students.