If an international student studying in an american school seeking no aid with GPA of 4, 5 in APs (8+APs) and 1500+SAT score ,athlete at National level and a sound musician, is seeking admission in the top 20 universities in the US at undergraduate level- are the chances really still only 10% .
Hello @TGK1248 - is your student a recruited athlete? And to help more, which sport?
No but represents the school- cross country and track.
For top schools, yes. It may be a hard cap or a soft cap. Few colleges will come right out (exception noted below) and say it, but many top colleges will limit international students to about 10-12%
MIT specifically mentions their cap:
http://mitadmissions.org/apply/international/howto
It depends upon the college, but the acceptance rate for international students at many top schools is roughly half the overall rate. So if the overall rate is 10%, the international acceptance rate will be around 5%.
Your chances will be higher than another international with a less stellar record. However, nobody can really put a percentage on it.