所以我想当老师用英文怎么说

"I want to be a teacher" 这句话可以用英语表达为 "I want to become a teacher" 。

来源：

"I want" 是一种表达意愿的方式，是英语中最常用的一种。
"to be" 是一个动词短语，表示状态。
"a teacher" 是职业的名称，在这句话中是名词性的。

例句：

I want to become a teacher. (我想当老师)
I've always wanted to be a teacher. (我一直想当老师)
Teaching is my dream job and I want to pursue it. (教书是我的梦想工作，我想去追求它)