In the first school scene the camera switches from facing the front of the classroom to the back of the classroom. Each time it switches the arms of the two main students in the scene keep going up and down. When the camera is showing the front of the students their arms are holding their heads up but when the camera is behind the students their arms are down.
The volcano experiment in the science lab involves mixing chemicals including nitroglycerin. It is very highly unlikely that high school students would be allowed to handle nitroglycerin (even in a highly diluted form) as they did during the experiment.
When Bianca Del Rio returns to Karma Johnstone's home the morning after escaping her abduction, behind them through the front door, a young man is visible walking past inside the house.
In the first classroom scene with Ms. Bianca, when Deborah asks Bianca to step outside, the sound effect of the box of chocolates being grabbed (and chocolates rattling inside) plays twice within a few seconds. The second time it plays it fits the visual (the first time it plays it is clearly out of place / matches no visual).