As much as the child is comfortable doing without too much pressure.
For a firm steady progress we encourage a minimum of 1 session per their grade. For example if your child is in grade 3 we encourage 3 practices a week. You will find that as your child becomes more competent, the rewards of practicing become more rewarding so they will want to practice more.
On the other hand we have students who never practice at all, yet they are still progressing, they still have fun and most importantly they still get a sense of achievement and increased self confidence. That alone makes music tuition worthwhile for your child. Eventually the spark does kicks in and then you can’t get them off their instrument.
Most importantly, the lack of practice doesn't necessarily mean they do not enjoy their instrument. It just may mean they have not yet developed the maturity and resilience to push through the tough stuff alone.
So hang in there, encourage but don’t force and never hesitate to call us for advice.