KANSAS CITY, Mo. - “Teachers open the door,” goes the old Chinese proverb. “You enter by yourself.”More and more these days, opened doors are at U.S. universities, and Chinese students are pouring through.This year, more than 98,200 Chinese graduate and undergraduate students were enrolled at U.S. colleges and universities, an increase of about 20 percent from 2008.Experts attribute it to several factors, not least China’s emphasis on academic achievement and the esteem with which the Asian giant holds American higher education.