WA Police Commissioner Karl O'Callaghan has renewed his call for parents to make sure they know where their children are at night, following two "out-of-control" parties in Rockingham and South Lake on Saturday night.

Police said more than 200 people attended each event and several people were arrested and charged after the South Lake party.

Mr O'Callaghan said there were three types of parents in these situations.

"There are parents who, when we take kids home to them, will be concerned and may not have known that their child was out or may have thought they were somewhere else and they'll respond and do something about it," he said.

"There are parents who know that their children are out somewhere and they don't care too much about it and then there are a group of parents who are simply not capable of looking after their children properly and so those kids are out on the street all the time and I guess a number of these would fall into this category."

Party organisers could be held responsible

Twenty-four police units attended the Rockingham party while eight units were sent to South Lake.

If charges are brought against those who held or organised the parties, they may be fined or potentially made to pay for the cost of the police operations.

The Rockingham party was held in a vacant building and had been advertised on Facebook.

Seven move-on notices were issued, and police transported seven children from the scene to their homes or a place deemed safe under law.

Mr O'Callaghan said child protection authorities had been asked to follow up with the parents this week.

"They would've been children that we had a particular concern about in that they were out there," he said.

"They were unsupervised and they were also in moral and physical danger, being exposed to older kids, and of course alcohol and drugs."

Parents need to 'get real'

The commissioner was particularly scathing of parents who drove their kids to the Rockingham party.

"I mean, you've got to get real, if you're going to drop your kids off at a party where you don't know who's running it, you don't know what's going to be there, you don't know what controls are in place, you are simply asking for trouble," he said.

"You're putting children aged between 12 and 16 into an environment where they're at high risk."

No charges have been laid over the Rockingham event, but police are still investigating.

Four people, including a 12-year-old boy, were charged after the South Lake party, which was held at a home.

The boy and an 18-year-old woman have been charged with assaulting a public officer after rocks and bottles were thrown at police.

Police removed four children from the scene.

Commissioner says more children need to be in state care

Commissioner O'Callaghan said police believed more kids in WA should be in state care.

"We all know there's about 2,500 kids in state care in Western Australia, most people will tell you there probably should be more like 4,000 in care so there's another 2,000 who are at high risk who could be moved out into care if it was possible," he said.

"So a fair number of these kids are the kids that we see on the street night after night, in physical and moral danger."

Commissioner O'Callaghan said matters were often complicated by family violence and alcohol and drug abuse.

"Sometimes those kids will come out of home because they feel unsafe in the home and the parents are in such crisis, they're not capable of providing support," he said.

"The problem with leaving kids in high-risk situations is they will grow up to have a whole series of problems themselves and what we'll see is another generational issue coming through so their families are likely to be in crisis as well.

"We're not talking about all the kids in Western Australia, we're talking about 4,000 out of many hundreds of thousands."