“How much should my child be practicing throughout the week?”
It's a simple enough question that, after 17yrs of teaching, I still find difficult to answer. But I’ll give it a go.
I expect students to include frequent trips to the piano as part of the rhythm of life.
Time spent on the instrument = you get better, but it is more important to maintain a consistent orbital path of returning to the piano.
I'll be more pleased to hear from a student who bumped into the piano every day than I am the one who jammed in a single 90min session just before their lesson.
While I like this answer, what most parents want to know is:
HOW MANY MINUTES?
So, never miss two days in a row and even if you think you don’t have time you have 5min. Anything less than double your lesson length throughout the week should land you in piano jail.
Piano players play the piano, every day.
Make music your lifestyle.