Mary, 44, of Rockville, clearly remembers the day her fourth-grade daughter, Lucy, came home in tears because her friend Charlotte had snubbed her at recess.

The duo had been inseparable since kindergarten - or so Mary thought - but recently Charlotte had started hanging out with the popular girls in the grade. On that day, when Lucy ran up to play, her one-time friend gave her a disdainful look and turned away without a word. After countless playdates, sleepovers and birthday parties, Mary knew Charlotte almost as well as her own child, and Charlotte's mom was one of her closest friends. What should she do?

"I decided that the girls were old enough to manage it themselves," Mary recalls. "Whether they were growing apart or having a break in their friendship, it was their business. As much as I wanted to call Charlotte's mom to tell her about the incident and ask what was going on, I resisted."

We all hope our children will build strong friendships in school and throughout their childhood. So when they encounter bumps in the road, it's tempting to intervene. Could it really hurt to suggest a playdate to your shy third-grader? Or call up a friend's parents to negotiate a truce in a friendship war? But that impulse risks robbing kids of the opportunity to solve their own problems and to experience the natural ebb and flow of friendships.

To be sure, when our children are toddlers and preschoolers, their social lives are largely structured around ours - we invite our friends' kids for playdates or arrange outings with families whose company we enjoy. But by the time kids are 5 or 6 years old, they start to develop true friendships of their own and may express a preference for certain children. That's when we should step back.

This is especially hard for moms like Madeline, 38, of Washington, D.C. Her son Leo made friends quickly in kindergarten, playing happily every day with the same group of four boys. They were all on the same soccer team, and it seemed a natural fit for playdates. But the other boys' parents weren't receptive. The quartet had been friends since preschool, and their parents all socialized together. There wasn't room for a newcomer.

Madeline empathized with Leo when he saw the boys bundling into the same car after school for playdates, and her heart broke when he asked to go with them but was denied. "It made me so mad," she said, "but I had to let it go. After you invite a boy for a playdate multiple times with no response, you really can't do anything else."

In these situations, empathy is often the most we can offer our children. They will surely have their feelings hurt in the future, so, in a sense, this is good practice. You can always point out that the adults are driving these friendships, without dwelling on the disappointment. They'll learn that they can recover from emotional pain, and they may even discover a new set of friends - building their ability to form bonds with peers. You never know what will happen as the boys grow up; they may begin to insist that their parents stop engineering their social lives.

"Empathize and join with your kid. You can say, 'When I was growing up, that made me sad too,' " says Dr. Julie Bindeman, a psychologist based in Rockville and mom to 8-year-old Nate, 4-year-old Jordan and 2-year-old Ryan. "I'm a big fan personally and professionally of working with your kids so they become their best problem solvers."

Talk through scenarios with your children to prepare them to approach new children at recess or in the lunchroom. Help them strategize how to handle the typical pushing and shoving of the playground.

Of course, if things turn violent, or your child seems to be involved in bullying, you may need to step in. "It can be a really fine line between friendship problems and what we see as relational aggression or bullying," says Bindeman. "Ideally, you have taught your child when they need to seek an adult's help."

Bullying is typically defined as repeated interactions between children who don't have equal social power. If you're hearing from your child that he or another child is frequently the target of physical or relational aggression, it's time for a check-in with the teacher, principal or counselor at the school.

"Say, 'Here are some of the things that I'm hearing. I'd love to join with you and figure out a way we can really promote a culture of nonaggression. How do we keep those values that we say we promote?' " Bindeman suggests.

As upsetting as friendship problems are, they are a normal part of growing up. As long as your child doesn't seem completely socially isolated or unable to interact with other kids, these challenges will likely help him learn empathy, develop new skills and avoid subjecting other kids to unhappiness in the future. "You can use it as a teachable moment," Bindeman says.

Don't get caught up in the culture of your school and push playdates on a child who isn't asking for them. Some children are happier in the company of adults, or perhaps they need more time alone to decompress, as compared with other children in your community. Often, the playdates you witness or hear about are as much a childcare convenience for the parents as they are an expression of deep friendships among the children.

As for Charlotte and Lucy, their friendship rift was permanent. Lucy sometimes speaks wistfully of the time they were close, but more often she's busy playing with her new friends. Mary hopes that the experience will help her daughter behave more kindly toward other children now and in the future. Most importantly, she wants Lucy to take away from the episode the lesson that she should befriend people who value her and who don't take her for granted or make her feel inferior.

"I've heard that girls' friendships can lay the groundwork for future romantic relationships, so I want her to expect to be treated well," Mary says. "If a friendship isn't reciprocal, it's better to move on."

Katherine Reynolds Lewis is a journalist, mother of three and a volunteer parent educator with the Parent Encouragement Program in Kensington.