How can I improve my studying skills?

When I was in Grade school, I usually topped. I used to top even when I don't study but sleep a lot. I passed in a special science high school for students with high intellect. So, I'm going to that school. But lately, I'm usually one of the students who have the lowest scores. In my past school, I don't study. I just have to listen to the teacher and I still top tests. But this time, even if I study, I still have low grades. How can I improve my grades? I noticed that if I listen to the teacher, the information isn't directly stored in my mind. In my previous school, even if I don't study I still have high grades. Help me!!! I'm quite alarmed. Thanks. ;)