Ride the short bus: (this is an offensive and insulting idiom) to be mentally or physically challenged. The buses used by public school systems in US to transport mentally disabled children are generally half the size (or smaller) of the regular buses, thus the “Long Bus” for regular kids and the “Short Bus” for the special-ed kids.

这个常用口语带有很强的贬义，不建议日常使用，但是你得懂得它的意思，当有人使用的时候你知道是什么意思。这个短语通常是用来指那些在智力上或者身体上有残障的人，它的引申义是用来指某人是弱智。这个短语的来源是在美国的公立学校里，那些需要特殊教育的学生（智障或残障学生）所乘坐的校车比一般学生的校车要短一些，于是当说一个人乘坐小校车就是指那个人有智障或残障。

造句：

a). That is a stupid idea and people would think you ride the short bus because of it.

b). You didn’t know who Barack Obama is? Did you ride the short bus to school?