Separate the sheep from the goats – 把绵羊和山羊分类， 比喻区分合格与不合格者或区分好坏。

例句：We had to sort out the sheep from the goat for the school choir. 为了选出能参加学校唱诗班的学生，我们把申请者分成了合格和不合格的两类。

中文里的“羊”成语

亡羊补牢 – better late than never

饿狼扑羊 – a starving wolf sees a tasty lamb and desperately tries to catch it. This phrase describes the action as fast, forceful and possibly desperate.

羊肠小道 – a long, narrow winding road

顺手牵羊 – walk off/walk away with something.

如果形容某人顺手偷走东西，则可以说 to have sticky fingers

挂羊头卖狗肉 – to sail under false colours 或者 false advertising