When parents should butt into kid's battles

Another kid is bullying your child on the playground.

Should you butt in? Not immediately, unless your child's safety is at stake. "If you're there, watch closely and give your child a chance to solve the problem on her own," says DeBroff.
The same goes for school: It's better first to equip your child with skills to stay safe and empower her to resolve the situation on her own. Realism: Good old-fashioned playtime
How to handle it: Rehearse ways for your child to respond. For example, if your child has a sense of humor, she can use a retort like "No, I'm not a baby, but thanks for asking," spoken in an assertive tone of voice. Otherwise, she can employ a strong "Cut it out" before walking away.
"Have her practice standing up straight, chest out, like she's wearing a bulletproof vest that taunts bounce right off of," says Borba.
When to reconsider: If the bullying persists and your child feels threatened, get involved. If you are the one intervening on the playground, nonchalantly pull your child out of the situation (snack time!) before discussing it. Talking to her in front of the bully could be more embarrassing.
If the bullying is at school, ask a teacher to keep an eye out. Most schools take bullying seriously -- 39 states have laws addressing it -- so teachers should have practices in place. To learn more, check out StopBullyingNow.hrsa.gov, which has suggestions for both parents and kids.