She used to teach them when they were children.
when they were children 是时间状语从句,修饰 used to teach,说明“曾教他们发生的时间”。它不可能修饰“人”。
She used to teach them when they were children.
【翻译】当他们还是孩子的时候,她曾教过他们。
如果觉得我的回答对您有用,请随意打赏。你的支持将鼓励我继续创作!

《高考英语备考1号·速效编》
《高考英语备考1号·写作编》
《高中英语晨读晚记》
《高中英语错题笔记》
《零起点考大学英语》