sentences:  The school also saw a decline in the number of foreign students enrolled as a result of stricter visa rules enacted following the deadly terrorist attacks of September 11, 2001.Roughly half of Thunderbird's students are citizens of a country other than the U.S.This makeup is a major asset to the school because students are immersed in a group of cohorts from all over the world, which helps instill the school's celebrated Global Mindset.