Cambridge is different from university at several levels. While in high school you have six or more mandatory subjects scheduled in a full day of classes. In college you usually take fewer classes with shorter lectures scattered across the week. Therefore, you have to become a good manager of your own time. Universities offer a myriad of activities and research opportunities that will consume a lot of your time if you are not careful.
Having said that, the intensity of a Cambridge program prepares you well for the workload of a university level. Many AS and A level classes will provide a solid foundation for the first college courses. For example, many of the studies I saw in my AS Psychology class were also part of my Introduction to Psychology course in college.
