“当教师”常见的英语表达有 become a teacher、be a teacher 或 work as a teacher，具体使用取决于语境和表达重点：
Become a teacher：侧重于描述成为教师这一职业转变的过程或结果。例如：
She dreamed of becoming a teacher since she was a child.（她从小就梦想成为一名教师。）
Be a teacher：直接陈述某人当前的职业身份。例如：
He has been a teacher for ten years.（他已经当了十年教师。）
Work as a teacher：强调以教师的身份从事工作，侧重于职业行为。例如：
She currently works as a teacher at a local high school.（她目前在当地一所高中当教师。）