True enough. For public exams, they normally use a bell curve/normal distribution graph to determine marks for grades and it changes every year. But I heard STPM is much stricter meaning the marks for grades don't fluctuate too much (year to year) and it's kept in check so as to maintain the standard of STPM.

In my opinion, most students have problems with Chemistry and Pure Maths and some neglect PA. PA is not a free A and you certainly can't get it if you just read the textbook.

Chemistry, like Pure Maths, the chances of getting a higher mark increases with the increase of exercises and practices you complete. So you are good for B and above if you have ;

1. Paid attention in class/to your teachers
2. Completed most of your homework
3. Studied at home and revised your lessons.

Oh yea. If you are taking Bio, it's quite difficult to get an A. I'm not sure as to why.

Get your teacher's help? Are they really that undependable? Or you can approach the tuition teacher and ask him/her whether he can conduct the class in a max of language so that you can understand?