Please check my writing? :)

Dear Sir or Ma’am

I would like to explain why I am applying for 10th grade as I am already being the 10th grade student. I consider my first year in America as the preparatory period for getting used to American lifestyle and its education system. I have done by best to adjust myself to the new environment, and I am getting used to new school subjects and the new surroundings. I would like to use this extra year in high school wisely so that I will be able to choose a college, which provides excellent academic opportunity.

Thank you.