Continuity mistake: When Rooney gets on the school bus, he crosses a grass boulevard with no sidewalk to board it. The bus never moves. When the bus pulls away, there is a sidewalk next to the bus where the grass was.
Continuity mistake: The dash or speedometer of the Ferrari is visible multiple times, but two different dashes are seen. In one the speedometer has a top speed of 160 (garage men speeding down the road, when Cameron sees the mileage is too high, and when Cameron sees the miles aren't coming off). In the other it has a top speed of 120 (when they get in the car to leave the garage, and looking over Ferris' shoulder at Cameron leaning on the car in the garage before he kicks it [open matte version]). The two dashes also use a different font for the numbers. (00:55:00 - 01:09:40)
Answer: Sloane knew it was a hoax. Ferris would not have done something like that without her knowing. Rooney pretty much had figured it out, but could never prove anything. Once he was discovered inside the Bueller house (illegally) by Ferris' sister, anything he did know he would have to keep to himself.
raywest ★
Sloane starts to put her jacket on the moment that she sees the school nurse walk into the classroom, suggesting that Sloane already knew she would be called out, and she smiles to her classmates.