If we could choose our children's friends, chances are they'd be surrounded by the smartest, sweetest, most nurturing kids at school.

Unfortunately, there are sure to be a few hurdles in the friendship space: Maybe there will be a super bossy friend, or a friend who skips school, or that dreaded friend who encourages your child to try drugs or alcohol.

Could you and should you — as a parent — break up that friendship? When is it OK to step in? And when do you have to trust that your child will figure out how to make the decision on her own?

When children are young, parents have complete control over their lives, and this includes their friendships, said Tara Pandarinath, a school social worker in Atlanta. At this stage, the child should be learning how to socialize, figuring out how to be a good friend, and should be supported in learning how to resolve conflict positively.

As children enter the preteen and teenage years, however, their job is identity formation, and friends are a big part of this.

"But you are still the parent, and your child is still learning," she said. "You need to set clear expectations about how your child should act, and support them in safely failing."

That may mean letting them be hurt in a friendship. That also means you have to be there to wipe away the tears and help them reach their own understanding about what it means to be a friend.

Toxic friendships, however, may need a different approach.

Pandarinath suggested approaching these with an attitude of curiosity, rather than an outright ban.

"Teens are very sensitive to authority, and it is developmentally appropriate for them to push boundaries," she said.

So while you can explain your concerns, don't try to manipulate or maneuver your child, because he will push back.

While parents have a hard time banning friends in the teen years, they can encourage their children to expand their social lives and to make new friends, said Christy Thrash, a licensed psychologist in Colorado.

"Parents can do this by signing their kids up for new after-school or church activities, or helping them find a part-time job where they will work with kids their age," Thrash said.

It's a different situation if your child is in potential danger from a friendship. A child's frontal lobes aren't fully developed, so they underestimate risks and may think they're invincible, said Kimberly Schaffer, a licensed clinical social worker in New Jersey.

"If the child continues to engage in the friendship after the parents have discussed their concerns, parents must do whatever they can to end the friendship," Schaffer said.

That could mean switching schools. This works if your child is being bullied and the school isn't taking corrective action, said Casherie Bright, a mental health counselor in Utah. It could also help if your child has made poor choices and needs a clean slate.

"I think that moving should be a last-ditch effort, however," Bright said.

That's because it's not guaranteed to work.

"If the child picks up a negative peer group and wants to be with the druggies because they feel accepted or feel like they belong there, they could possibly just find the same type of kids at the new school," she said.

Since a perfect school doesn't exist, children need to be armed with the strength to resist temptations and peer pressure regardless of the setting, said Donna Aucoin, a licensed psychologist who works with children, schools and families in Lafayette, La.

Fostering an open and honest communication style with your child and educating her about drug and alcohol use, risk factors and addiction are helpful, said Kelley Kitley, licensed clinical social worker in Chicago.

When your child is associating with a more positive group of friends, it's important to reward that behavior.

"Increasing supervision and structure at home when their kids make bad choices, and then allowing them more freedom when they make positive choices, will go a long way in fostering a healthy amount of independence in teens," Thrash said.

It may also convince them to make friends that make both of you happy.