Well, I like the image you posted and I think that there is a big difference between high school and university.
The hardest thing for me was to get used to new professors and try to fit in. As a pupil you have a homeroom teacher who knows all your problems and you can always talk to him if you have any complications or misunderstandings with other teachers. Me and my schoolmates had a really good relation with our homeroom teacher and we talked every day. Suddenly you're at the University where you no longer have the person 'who is responsible for your behaviour' and it's hard to accept.
As for the rules-they are very different, too. In high school, teachers watch every step you make and wait for a mistake :) If you're restless during the class, a teacher will throw you out , write down your name in the book and probably send you to visit and explain yourself to a headmaster. University professors have a distinctive approach and if you're a talkative person they will probably just tell you to calm down and lower your voice because you're free to go at almost any time you want.
Also, highschool teachers must always know where are you or where do you want to go during their class because they have to keep files about the pupils.
I mustn't forget one of the main things-books and learning. I don't think I need to explain because you all know what it is about- too much material to study.