one possible version:

Dear Mom and Dad,

The annual University Entrance Examination is around the corner. On this special occasion, how I wish I could have a heart-to-heart talk with you.

Throughout these years, I always feel grateful to you for your unfailing help, care and love. I have been making remarkable progress in my studies thanks to your constant encouragement. It’ll be no more than one year before I take the University Entrance Examination, which makes me under greater pressure. I need frequent support. Good learning conditions and timely help from you will do me a lot of good.

Mom and Dad, my dream is the very one you always have. I’m fully aware of the responsibilities I am bearing. I plan to make a detailed study schedule for this coming examination so that I can review lessons and practice solving problems of different subjects. It is also necessary that I do some physical training once in a while so that I can keep fit. If possible, as a family member, I will also help do some housework to make you relax a little bit.

I am quite confident of my study. I do wish you good health and a happy life.

Yours ever,

Li Hua