I just graduated from high school last year and got an A-( in Kenyan national exam). Am preparing for SAT due October. Am confident for a perfect score. Will that help my application to these top-tier institutions?
There is not enough information to say. Getting into those colleges requires far more than excellent test scores. For an international student, you would need to be one of the top handful of students applying from your country, not only academically, but in terms of awards, extracurriculars, letters of recommendation, etc. Test scores alone will not tell us if you are one of those top 3, 4, or 5 students.
Thanks a lot. That’s an eye-opener
I agree, as an International Student to these schools, they expect the best ec’s and also don’t expect them to give you money or accept you if you qualify for financial aid… I saw someone apply for aid and since that can be used in selection process, he was tossed from most schools.
^ Not the full picture, @tchit87. What you “saw” is anecdote and you can’t know why anyone was rejected, the content of their full app and supp.
Many top colleges do offer aid to internationals. But the competition, as @Groundwork2022 noted, is fierce- and more than just stats.
OP, because these colleges review in a “holistic” manner, it would help you to learn what they do value and look for, what they say and show, in therr web sites. Then you can try to “self match,” see how you meet what they want. Not just colleges that attract you.
You need more info for us to help you 
I think that MIT is need blind for all students, including international students. Caltech and Stanford may consider your financial need when deciding whether to admit you. I am pretty sure that all three of these schools do provide need based financial aid for international students. I don’t think that any of them have any merit based scholarships at all. You would need to apply for need based financial aid at the same time that you apply to the schools unless you can afford to be full pay for a full four years.
One way to think of this is that all three of these schools might admit one or maybe two students from Kenya in a given year, or they might (more likely) not accept any.
Admissions is hard to predict for the very top students. A perfect SAT score will help, but will not by itself get you accepted.