I want to be 用法

问题描述:

I want to be 用法
I want to be a teacher.
She wants to be a teacher.
They want to be a teacher.他们想成为老师
请问这样写对吗?They 作主语,是写to be a teacher 还是to be teachers?

They want to beteachers.
They 作主语,应为复数