at a level one of my chemistry teachers was excellent, the other didn't even know the chemistry he was teaching us (taught us an entire topic not on the syllabus, asked us a question and someone gave a wrong answer as a guess, he said it was right and i corrected him, he played it off that he was testing us but it was obvious he had no clue, whenever we asked him questions he had to look up the mark scheme for the answer, etc) we hated him, but we all got by because we went to see the good teacher for help on the bad teacher's topics. i'm going to uni to study chemistry and another girl from my group got accepted to medicine!! so please know that no matter how bad your teacher is, you can still push through and get the grades, just do loads of past papers and ask any chemistry teacher if you need help, i'm sure they'll be more than willing to sit down and explain things!! good luck!!