When Auggie gets off the bus after the trip to the nature preserve and is with his Mom, a blonde Mom in the background to the left is seen walking behind them from the same spot twice.
In preparation for his graduation, Owen Wilson's character knots Auggie's tie with a simple knot, but later at the ceremony, the tie knot is the more elaborate Windsor knot.
When Auggie's dad drags the Christmas tree out of the house, the tree is held by the bottom in the first two shots; in the third shot when the tree is almost through the door, the tree is held by the top.
Via first meets Justin in the hall and have a short conversation. Justin supposedly subscribes during their conversation. However, his name is already filled in on the subscription form.
In the month of February, there are green leaves on the trees; the film takes place in New York.
At 19:50, Newton's first law of motion is being taught in Vth grade which is taught to high-schoolers.
After the New Year's countdown, Isabel's laptop shows the time 10:00 p.m. It should be 12:00 a.m.
When Isabel is typing on her laptop computer during the Christmas/New Year's Eve montage, the date on the computer screen reads April 3rd.
After the fight between the five Beecher Prep boys and the two seventh grade bullies at the Pennsylvania retreat (at 1:36:35), as Henry says "They were huge!", he throws both arms up, lifting his sweatshirt to reveal the black cord to his microphone.
Homeschooling blackboard contains a solution that has nothing to do with the equations and the equation systems above it. Seemingly it is the solution to the equation system {3x+2y=-4, 2x+3y=4}, but in fact it requires a different method to solve, and its solutions are x=-4 and y=4.
The Wizard of Oz is being shown in the wrong aspect ratio; it is shown filling the entirety of a widescreen. This would not be possible without cropping the image or stretching/distorting it.