Check out this article to learn more about guardianship: What's a Primary Guardian? What's a Secondary Guardian?
Some coaches offer Gold Memberships to students through their programs or clubs. To assign the Gold membership, they need to be the Primary Guardian of the Kid account. If your child would like to continue using the same account they've been playing with, you'll need to switch the Primary Guardianship of the account to their coach.
Switch Primary Guardianship
From your Parent or Coach account click on Manage in the menu at the top and select Kids:
Click on the icon next to the Kid account you want to update the guardianship of and select Edit Kid:
On this new page, scroll down and click Edit Guardianship:
Here you can view your Kid's teacher or coach, or add a new one by entering their email and assigning them an appropriate guardianship status:
If you make them the primary guardian, the coach/teacher will have the ability to assign your Kid a Gold membership, and you will still see them in your My Kids list.
If you wish to completely remove the Kid from your My Kids list, you can click Transfer Guardianship, which will transfer the Kid account entirely to the Coach/Teacher.
Click Save to apply the changes!