They need to learn to stand up for themselves
How often does your kid talk to their coach or teammates and stand up for themselves without parent input?
It’s crucial you teach them how to do this while they’re young. Not only will it benefit them now, it becomes necessary at high school anyway as coaches generally don’t want to be dealing with parents and for sure at college, students are expected to completely advocate for themselves.
Empower your kid to do it on their own
Next time your kid has an issue on their team or in school, encourage them to ask questions and try to deal with it themselves. It’ll be hard and uncomfortable for them but over time it gets easier.
They won’t learn to advocate for themselves if you constantly step in and try to resolve difficult situations for them. The only way they will learn is by struggling through and figuring out how to do it for themselves (of course you can offer guidance and support).
Don’t wait. Get them started now.