That number—12.9 percent—may not seem remarkable, but it was: Kids in San Jose whose families fell in the bottom quintile(五分位数) of income nationally had the best shot in the country at reaching the top quintile.
那个数字——12.9%——可能看起来并不显著,但它确实如此:圣何塞那些家庭收入在全国处于最底部五分位数的孩子,在达到最顶部五分位数方面,拥有全国最好的机会。
限制性定语从句,修饰主句主语 "Kids","whose" 在从句中作 "families" 的定语,限定了这群孩子的家庭经济背景特征。