Lawyers for juveniles sent to an adult prison after a riot at the Banksia Hill Detention Centre say boys as young as 14 have been subjected to brutal conditions.
Up to 70 juveniles are being held at Hakea prison after they were moved from Banksia following the riot in January.
Shine Lawyers' George Newhouse says the juveniles have been unable to see their parents, they feel afraid and they have lost access to a range of educational and psychological programs.
Mr Newhouse says the children's parents are worried.
"They are asking that the conditions of these children be reviewed and that they be placed in a humane environment where they can access proper programs and rehabilitate," he said.
"They should not be in an adult prison."
The Department of Corrective Services has defended its treatment of juveniles in Hakea Prison.
It says while the new juvenile unit at Hakea is not ideal, it is separate from the adult prison.
The department has also denied reports detainees have been subjected to long periods of lock-downs, have been underfed, abused by prison guards or had lost access to rehabilitation programs.
Meanwhile, an inquiry into the riot has heard from the WA Commissioner for Children and Young People.
In her submission, Michelle Scott says the juvenile justice system lacks cohesion.
The Commissioner says WA had one of the highest rates of juvenile detention in the country, with centres continuing to work at or above capacity.
Ms Scott says the system is not working and she is calling for better cooperation between agencies and immediate action.
"While there have been some positive steps in the last few years, there haven't been enough steps and we need to do a lot more to start taking this issue seriously in our community," she said.