Learning how to produce work doesn't happen overnight. Yet determining why quality is important can be equally challenging task.
Even if you expect quality, you may need to give your child time to work up to understand why quality is important.
Learning why is the first step. Doing competent work follows next. Once your child can prove that he can do competent work, a commitment to improvement is what will lead to quality.
What you need to do is to encourage this process, but don't mandate it. Guiding our children to do quality work because it ultimately improves their lives is the reason to do it. Making it more enjoyable should be the goal, and never just because "I" say so.
