Don't care what others think, and don't think about your environment. As long as you have a strong desire to get good grades, you have the possibility of success.
I can only have some suggestions for your reference. First of all, you can make a plan, which should be detailed and specific, and list your long-term (that is, college entrance examination) goals. I think this goal must be higher than reaching the key undergraduate course. For example, it can be set to exceed one line by 20 points, which is your ultimate goal. Write it at the end of this page, and then list your short-term goals step by step. I don't know what your ranking is in the class now. If you are in the middle of your class, your goal is to get into the top 10 or top 5 in this final exam. The goal must be set higher, but not beyond your ability. So according to a-> b->; C the way to achieve your goals one by one is just like playing a game to complete a task. But please note that this is realistic learning. If you fail, there is no chance to come back, so if you really make up your mind to be admitted to a key undergraduate course, you must put pressure on yourself.
There are too many learning methods at ordinary times, but no matter how good they are, they may not be suitable for you, so I think the best learning method is your own exploration, but you must pay attention to one thing: always keep a tight heart. If you are lazy or like to play, then I suggest you take a week to play enough. After a week, you should be a person who keeps his promise. This promise is that you are responsible for yourself.
Believe in yourself, no one is born poor. Don't think of yourself like this in the future. Say to yourself: I am a key undergraduate, and I am different from others. You can do it if you want to.