vocabulary

Telling would be a more appropriate word than advising.

Yes… but an article would be better: Advising children to behave well is the parents' duty. / Advising children to behave well is a parent's duty. (Note the apostrophes.)

Thanks for your answer

sorry dear
I have one more question
when I write these sentences in the Microsoft word It underlines the auxiliary verb "is" with a green line, and asks me to change it to "are".Why?
Advising children to behave well is a parent's duty.
Advising children to behave well is the parents' duty.
as follows
Advising children to behave well are a

The simplest and most natural way of wording it would be "Telling children to behave well is a duty of parents".

Thanks so much for your patience and your answer