1. Take notes, especially in chemistry and English. Go home and read your notes even if you don't study.
2, more summary! Summarize some regular knowledge, especially science, which is very regular!
3, to do more exercises, I study science, there are many exercises at home, if it is really not good, go online to find questions to do!
I suggest you buy the above explanation (Zhihong's question). I think it's ok, but there are fewer mistakes. Now I buy it every semester as a master of science (mathematics).
Well, anyway, you have to work hard in high school. Come on, O(∩_∩)O~