Chinese and English are basically not needed. If you are weak in some aspects of English, you can buy special training exercises to do it. Mathematics and science are basically handed down by teachers, but I can't.

Tian Li will be better, but I personally don't recommend buying it, because if you want to finish all the school exercises, there is basically not much time left to do extracurricular exercises. Last year, most people in our class bought it, and few people did it, only less than three people did it. So it is not recommended to buy it, it is too wasteful.

If you want to buy, you can join the whole class or several classes to buy together (voluntary registration), which will be cheaper.