I am going to immigrate to the United States, and I will go to the United States to study and take the college entrance examination in the future. What's on the SAT? Is it optional?

Harvard is not an exam, it is an application.

Pay attention to your usual grades. Three years in high school is better.

And your interests, extracurricular activities, awards and so on.

You don't have to study science, but Harvard has many liberal arts.

The Sat is only a reference, and high scores are not necessarily accepted.

Chinese is not good. Your mother tongue is Chinese. Chinese majors don't teach students whose mother tongue is Chinese.