The New Kid - S1-E2
Other mistake: At the start when the gang change the time on the clock in the classroom, it wouldn't control the main school clock, plus in every other episode the clock has been operated by The Box on the side of the school, as shown in " The spy who came into the playground".
I Will Kick No More Forever - S1-E11
Other mistake: When the gang go to visit vince in his house, it shows vince watching a video of a kickball game. but kids most definitely wouldn't be able to bring a video camera in to school, and it most probably would be confiscated by miss finster.
Other mistake: In the episode, "the peanut butter kid", he is always eating his sandwich and it always seems like he only took a bite out of it and sometimes it went all the way back to the top. How could that be, he couldn't be chewing the entire time.
The Spy Who Came In from the Playground - S4-E4
Other mistake: When the gang is showing stone their way into the school they go through a vent and all of them manage to squeeze through the small hole in the wall.
Other mistake: In this episode when Spenilli passed the test,she busted out of the school, you can see the school clock has no 5. Whats up with that?
Beyond a Reasonable Scout - S5-E3
Other mistake: Phil the Scout ties a rope to Mikey's see-saw end's handle to lower Gus down without hurting him. Couldn't Mikey just climb off and hold the see-saw down with his hands and lowered Gus's end down slowly?