Are you sure you're asking about advantages instead of methods? In fact, you should consolidate your junior high school knowledge now and get a good grade in the senior high school entrance examination first.

If you have a good foundation, your advantages are time and adaptability. If you had entered high school earlier than others, you wouldn't have such a big gap, and you would get used to it soon. Math in senior high school is still very important. One step ahead of others will give you a little more advantage. I hope it helps you ~