Without regular practising, there is no progress. Ideally, a child should have a regular practice schedule of about 15 minutes a day, for at least 4 days of the week. Cramming in a long session just before the lesson is never going to be successful. If possible, the child should have a quiet space to practise, with no TV or computers on. If you are able to supervise the practice for a couple of sessions, progress will be faster: in any case, you should aim to hear your child play the piece(s) at least once a week. Parents have to persevere too, often through gritted teeth and fixed smiles!