Is there a necessary connection between high school mathematics and IQ? ....
No, high school mathematics is almost like that. The key is learning methods. I said slowly: Do you find that math teachers often talk about examples? Remember, it is best to write down ideas (notebooks must be ready). The topics on the test paper are similar to the types of examples. Of course, you don't have to remember every topic, and you don't have to repeat the same topic. Practice more in peacetime. In fact, having said so much, it is still an old saying that people who like mathematics study well because they are willing to spend time and energy. High school math is like this. Not if you understand it. You should practice more.