When Mr. Bean enters the classroom in the exam sketch, there is a desk in front of the one he sits at. But after the exam begins, it has disappeared.
During the exam, the man who sits next to Mr Bean to do his exam you can clearly see he is just scribbling along the paper and not actually writing anything.
When Mr Bean takes out the green exam paper out of the envelope, there is no writing on it.
When Mr Bean reverses into his spot outside the examination hall, a group of crew members is visible pushing the camera reflected in the car nearest to the camera. More noticeable as the camera is actually moving.
When Mr. Bean is backing into the parking space and knocking the blue car out, you can see the camera and crane reflected from one of the car's side windows.
In the first scene with the exam, one of the extras in the first row looks directly at the camera as it pans over him.