Eight classes a day
Normally, on an average day at an American school, you would have 8 classes. Seeing as school starts at 7am there is quite a lot of time to fit everything in. This is pretty different to most of the rest of the world, who try and cram fewer classes into one day and spend longer in each focusing on a topic.
The assumption is that more classes mean shorter classes and, seeing as a teenager’s attention span is pretty short, this helps with learning and stops boredom. Other countries would probably argue that their way is better, though.