I'm 18 years old and I'm a Sri Lankan. Am I too late to get ready for ivy league? and how are my chances of getting in?
So it's very hard to answer this question considering you told us nothing about your profile. But the ivy league is very hard to get into. You need to have high test scores, GPA, stellar activites and essays, etc. It is not to late to get ready for it and if you're applying this year the only thing you can really do to strengthen your application substantially is to start working on your essay.
Your chances are very little, mainly because you are an international student. However, look to a smaller, state school in the US. This way you will be able to get a quality education without spending too much money.
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For international students state schools could be more expensive because they are not eligible for federal aid. However, a lot of private schools will provide them financial aid, so going to a state school might be more expensive for them.