40% of UC students are asian (and it's higher at Cal, UCLA and UCSD (i.e. the better schools)).[1]
23% of Stanford students are asian (probably higher since that excludes "international" and "decline to state").[2]
26% of MIT students are.[3]
In other words, at (a small sampling of) the top schools, Asians are over-represented by anywhere from 400% to 1000%. It just doesn't seem like any sort of quota system exists, looking at the data.
[1]http://diversity.universityofcalifornia.edu/documents/divers...
[2]http://www.stanford.edu/dept/humsci/external/under/demograph...