What is the age of the girl in the poem 'Amanda"? How do you come to know her age?

Amanda is around between 9 to 10 years old school going girl. We come to know about her age from the fact that her parents are trying to inculcate good habits in her. But she is very innocent and immature and does not really appreciate the nagging done by her mother. She still gets instructions from her mother to do her homework and tidy her room. So, we can say that she is a young girl.