I'm a senior, and I'll be taking the SAT for the last time this coming November. I will also be taking the Edexcel International GCSE in January; I decided to take the five main subjects: English, Mathematics, Biology, Chemistry, and Physics, only. Because the deadline for the University I want to apply to (the U of M) is the 15th of Dec., I'll have to send my Sat scores right away, but I wouldn't have my high school transcript. Even if I attached a letter notifying the date at which I would get my results, what would I use in place of the high school transcript. Needless to say, Sat scores alone wouldn't be enough to determine my capability and acceptance to the University. This is especially true by the fact that I don't score high in the Sat (previously I got 440CR, 550M, and 560W). Anyhow, I am confident that in this coming Sat Test my scores will improve drastically.
I am a citizen of the US who is living in a foreign country and planning to return to the US for University.
Main question: As in my case, what can I do to increase my chance of being accepted to the U of M?