Actually i’m a grade 11 student in egypt, i score 1420 in june,2015 SAT ( 390 CR, 570 Maths, 460 W (8 essay )
i have to improve my score during a time frame of One months and 3 weeks, i must score +1900 to be accepted in the medical school. WHAT SHOULD I DO! and is it possible !!?
Yes, for CR ones: I think u are missing a lot of SC questions right? Buy Direct Hits and study it hard, it should improved your scores by high 500s and 600s low if u got approximately 1 wrong questions in the SC sections.
For the Math section: Buy Dr. Chung Math and dig hard in it, once u got the hang of it, it should be no problem to be scoring from high 700s to a perfect 800
For the writing section, buy Erica Meltzer Writing book, it’s a really good book if u wanna increase your writing score, by up to high 700s, so there u have it, u may even get a 2000 in the october test 
Hope this help
its not as easy as it sounds^
but its possible…
but you’ll need to put min. 5 hrs a day