Five to seven is generally the age at which many children first take up the guzheng. At this stage hands can manage short practice sessions and attention spans can sustain them, and children already have a basic sense of pitch and rhythm.
What matters at this age is not how long they practise but how regularly. Twenty to thirty minutes at the same time each day builds a habit far more easily than a two-hour session once a week, and is less likely to provoke resistance.
Practice can be split into blocks: a few minutes of basic technique, a few minutes of a piece, a few minutes of rhythm or sight-reading. Solving one or two small problems per session gives the child a sense of having made progress today.
A parent’s role is company and reminder, not correcting hand shape in place of the teacher. When a child gets stuck, note it down and hand it to the teacher — usually more effective than repeated correction at home.
Whether to practise every day, and for how long, ultimately depends on the child’s age, school workload and interest. There is no need to compare with other children.