The quality of the work you do also changes. It is not enough to understand course material and summarize it on an exam. You will also be expected to seriously engage with new ideas by reflecting on them, analyzing them, critiquing them, making connections, drawing conclusions, or finding new ways of thinking about a given subject. Educationally, you are moving into deeper waters. A good introductory writing course will help you swim.
This explains how different doing work from high school can be to college. For example college expects you to seriously engage, analyze, critique, make connections, and drawing conclusions. Unlike high school it is not enough to understand the course and just summarize it on a exam.