Put the verb «to be» in Present Simple:
I a pupil. I at school.
My brother a painter. He not an engineer.
My sister at home.
We not at school. We at home.
My sister at work. She a doctor.
Mike a student.
you a student? – No, I a doctor.
your sister a teacher? – No, she a student.
Nick and Peter little children. They not at school, they in the kindergarten