Many parents will, at some point, be concerned about the influence of their child's friends.

Melbourne provisional psychologist Dr Charlotte Keating said it was natural for parents to want to control who their child is pals with.

"Parents on the most part have good intentions and they simply want the best for their children," she told 774 ABC Melbourne's Clare Bowditch.

"They want them to be safe and they want them to form positive relationships."

She said parents could act as a "social secretary" for younger children, but that changed by the time the child reaches grade six.

"The capacity to choose who your children are friends with ... dwindles as they get older," she said.

Give children space, encourage them to talk

Once a child is in early adolescence, Dr Keating said it was important to step back and allow them space to make decisions for themselves.

"It's important not to helicopter or orbit your child too closely ... because they are more likely to be secretive and hold things back from you."

Maintaining an open and honest relationship with your child will help you spot when they form a toxic relationship.

"That comes through knowing who your children are friends with, having the friends come over to your house so you can actually observe the relationships," Dr Keating said.

It was important to talk to your child if they seemed upset after spending time with a friend, she added.

Dr Keating suggested starting such a conversation by saying: "You seem upset when you come home from so-and-so's house, what's been happening, what's been going on?"

"Then it becomes a focus on the sort of behaviour that might be making them upset rather than necessarily the personality or the child."

Encourage children to follow their passions

When a child reaches high school, Dr Keating said, they become more likely to form friendships with children their parents preferred they did not.

"Adolescents are wired for a little bit of risk taking."

Dr Keating said if parents were worried about a particular friend, then a good tactic was to "dilute" the time they spend with them by having more children around at the same time.

Another way to help a child form positive relationships was to encourage them to follow their passions.

"It's really looking at what your child's strengths are because their strengths are what they are likely to be quite passionate about," Dr Keating said.

"You can then get them involved in those passions, be it art, drama, music or soccer.

"Not only are they meeting likeminded people ... but they don't have so much time to get involved in cheeky behaviour."

Set an example with your own relationships

High school friends are one thing, but can parents exert any control over their child's romantic partners?

"No," Dr Keating said.

The best hope parents had was to model good behaviour, she said.

"Bring your kids up in an environment where you have trusting, respectful relationships with your partner and you have friends that you have around to the house so your children are exposed to what good social relationships should look like.

"Then you're doing everything you can to set the foundation for them to then choose similar relationships as they get older."