I'm sorry I haven't written for so long because I've been busy at school preparing for my exams, but I was happy to get your letter.
In your letter you say that you haven't done very well at school. You can do better at school, but you must make more efforts. I think you should talk to your parents and explain how you feel. I'm doing very well at school, but sometimes I've some problems.
Why do you fail? What do the parents say?Why are they angry?