The first non-introductory scene is a 3 on 3 swim meet between Macdonald Hall and York Academy. When the race finishes, Boots is shown as being alone when he reaches the end of the pool, yet the scoreboard shows 3 swimmers finished before him and 1 after (one failed to start), none of which are anywhere to be seen except the one who didn't start.
The first non-introductory scene is a 3 on 3 swim meet between Macdonald Hall and York Academy. One swimmer fails to start - presumably from the inexperienced Macdonald Hall (this scene existing only to portray their inexperience) - leaving 5 swimmers, who would be 3 from York and 2 from McDonald Hall. But at the end when Boots looks up at the results, he is the only swimmer from Macdonald Hall, the other 4 places listed as York, when they only would have had 3 swimmers racing. When the York team snubs Boots later, there are indeed only 3.
When George Wexford-Smythe III takes Bruno and Cathy to his rich kids' club, the scene starts with Bruno and Cathy walking alongside George riding his segway. However, as they reach the door to the club, it can be seen that directly behind their starting point the landing ends, beyond which the top half of a door can be seen, indicating there's a downward staircase there leading to said door. George couldn't have ridden his segway to this point as is depicted.
When the movie first shows Bruno & Boots' room, Boots is on a video call with his mom. She is seen hanging up the call by poking the screen, however this would mean she poked the camera, which is not where any device's hang up button would or could be.