Hi, SAT is an internationally recognised standardised test that evaluates a candidates knowledge in reading, writing and quantitative aptitude and other specialised subjects. SAT is taken for undergraduate admission in the United States and some other countries.
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Hi, Yes it shall affect your academic performance in school. Though it varies in universities abroad as all have their own parameters. One has to aim for high grades in school specially class 10th, 12th. Apart from this partcipation in some extracurricular activities in the school or even outside shall help you to build up interesting profile. If you can get recognition from some sort of national or international competition (esp. international olympiad or international research competition), that will help your chances a lot. So this is how much it matters.

• Learn to be extremely picky about which answers to eliminate. This especially applies to the Reading and Writing sections. If a question seems subjective, keep reminding yourself that its an illusion. All incorrect choices are incorrect for good reasons, and its your job to find those reasons until you narrow your answers down to one possibility.
• Look for words that indicate positive or negative connotation in the part of the passage that the question references. This can help you to eliminate at least a couple of choices even if you have no idea which of the remaining choices is correct.
• At the beginning of every passage on the SAT, there is a little italicized blurb giving you a bit of context about the passage and its author. This introductory blurb contains valuable information, and if you skip it, you could miss out on easy points.
• SAT questions are not arranged in order of difficulty (so that easier problems come earlier in the test than the hard ones). Instead, its important to identify the questions that YOU find easy or hard.

If you are willing to give SAT test 2017 with Essay the registration cost would be US $54.50 and if you opt out of the Essay, since it is optional, your fee would be $43. For international students taking the test outside US, an extra $49 is added to the registration fees. For SAT subject test, the basic registration fee is $26. Aspirants have to add $26 for language tests with listening and $18 for other tests.