What will going to a Korean school be like for a white girl?

It will help that you can speak Korean well. Work on it this year and try to be fluent. Learn to read it too. I am not going to kid you-- some kids might be bullies. But I am sure that you will be able to meet some nice kids, too. Besides school, you might also meet other kids at church and maybe your host family can introduce you to other kids. Believe in yourself and try to learn as much as you can. You will still be going to school there.