How Often Should a Junior Golfer Practice?

There's no single right answer, but age, attention span and enjoyment should drive the schedule more than a fixed hours-per-week target.
Shorter and more frequent beats long and rare
For most junior golfers, two or three short sessions a week (20-40 minutes for younger kids, up to an hour for older, more committed juniors) will build more consistent progress than one long weekend session. Golf asks a lot of fine motor control and focus, both of which fade quickly in children - a tired, distracted 90-minute session often teaches worse habits than a focused 25-minute one.
Mix skills instead of only hitting balls
A practice session doesn't have to mean standing on a range hitting driver. Putting and chipping around the house or backyard, working on grip and stance without a ball, or simply throwing and catching to build hand-eye coordination all count as useful golf practice for a young player - and they're often more accessible day-to-day than getting to a range or course.
Let enjoyment set the pace
The single biggest risk with junior golf practice isn't doing too little - it's turning practice into a chore that kills a child's interest in the game. If a scheduled practice session is met with reluctance most weeks, that's a signal to scale back frequency or change up the activity, not to push through it. Junior golf pathways (like MyGolf) are deliberately built around games and fun rather than drilling for exactly this reason.