Help! International Grades for Brazilians

<p>Hey,
Well, I am a brazilian student that dream about studying in the US. I have started thinking about it after a man gave a lecture in my school about studying abroad. After that, I started researching like crazy about it, took the SAT once just to see how well I am and how much I should get better (have already bought the blue book and i'm studying a lot).
My big concern is about the grades. Well, there is still a long time for me untill college since I am in my first year of High School here (that would be the sophomore year in the US). I do some good ECs with good "depth" in it and I'm planning to start even bigger and better projects. The thing is: I do a special High School program offered by Texas Tech University (I know it is not a big deal but anyway...) to the best students, which gives you an american high school diploma after you finish it, and it has been great, but after talking to one of my teachers, she showed me the grades stuff. Man, I got really scared. Here in Brazil our grades are given in numbers instead of letters, and even the smallest mistake can take you 5 points out of ten. That's enough to make your A become a B+. and it is not the whole question; let's say my test has 10 questions and each question has 5 sub-questions. Yeah, one wrong answer is enough to destroy the shiny A. And also, I have this american girl that is in my class. She lived her whole life in the US and got here in Brazil this year. I talked a lot with her about this school stuff and all, and she said (and I noticed it), that the high school in the us is much easier. I'm not being rude/ snobbish , i'm just kinda curious.. You can choose your classes? WTH! I wish i could choose my classes! Here we take advanced physics & chemistry since the first year... no options and i have sociology, philosophy,literature, biology (really advanced things, this girl has never seen anything like that in her whole life lol, and she's not stupid, not really)...etc. This girl i talked about, when she got here, she showed me her math notebook of the subject they started learning just before she moved. It was the subject we learned one year and a half ago, and untill today she doesn't know our subject because it is too advanced. i go to school 7:30 in the morning and get out at 5:30 pm, sometimes 6:30 pm, all my free time goes into ECs. I'm not saying brazilian education is better, NO, I'm just worried because it is literally IMPOSSIBLE to take A in all subjects, and after reading some threads here on CC, i have found some people saying that international students usually go to 2nd or 3rd tier school because of GPA. THATS NOT WHAT I WANT FOR MY FUTURE! I swear for everything i know that in tests week i study 5 hours a day, and still get B-! This B- makes me the best of my whole class....
Anyway, Supposing i have plenty of good and important ECs that i love to do, i'm the best of my class always (that in brazil is absolutely awesome,but in pure, raw grade converted to the US system is not THAT good), write a superb essay and take a good SAT grade, what are my chances of entering schools such as UT-Austin, UW-Madison,UVA, UMich and UPenn?
Also, here we don't have ANYTHING like student organizations (so i could join or be president, etc), big sports groups (only for soccer, and it is absurd how competitive it is), AP Classes (that would help me a lot, but we dont have it), We must do ECs by our own, the schools doesnt help anyone... So what kind ECs would help me to stand the competition? I mean, to get in great Universities sch as those ones i said.. It might be a dumb question, but i'm really disorientated alone here...
Sorry mates, i didnt want to look/sound harsh or mean, really, im just so preoccupied about it... Thanks guys!
:)</p>

<p>[EducationUSA</a> | Study Abroad, Student Visa, University Fairs, College Applications and Study in the U.S. / America](<a href=“http://www.educationusa.state.gov%5DEducationUSA”>http://www.educationusa.state.gov)</p>

<p>Read through the website, and contact the counselors at the advising center closest to you. There are many in Brazil: <a href=“https://www.educationusa.info/Brazil[/url]”>https://www.educationusa.info/Brazil&lt;/a&gt; The counselors are expert at helping students like you find good places to study in the US.</p>

<p>Okay man, thanks for the advice! :)</p>