The grandmother of a Banksia Hill detainee set to be transferred to an adult maximum security prison said her grandson had been pepper-sprayed, zip-tied and was often sedated in the juvenile detention centre.

Noongar woman Pam Blurton joined a protest march in Perth last Thursday against the plan to send about 20 children from Bankia Hill to Casuarina.

Ms Blurton said her grandson was the 15-year-old boy who Children's Court president Hylton Quail described as suffering "prolonged systematic dehumanisation and deprivation" in Banksia Hill.

"(My grandson) told (his sister) last week that he was pepper-sprayed and detained with zip-ties, and put in the back, in what they call the fish bowl," he said.

She said he was often sedated when she visited.

"One time I went in to visit and he was not sedated, he was really angry, he started throwing chairs and he climbed up towards the windows to smash them.

"His sister climbed up there and held him, gave him a hug and he started crying."

Ms Blurton said her grandson was "not an angel" but she had hoped he would get help at Banksia Hill, and was now fearful for his future at an adult prison.

"They need Aboriginal people hired to work with them," Ms Blurton said.

"And when they get outside, there is nobody and nothing for them. They don't have professionals to work through what they have been through in there."

A WA Department of Justice spokesperson refused to comment on individual cases.

"Chemical agents such as capsicum spray are rarely utilised on young people at Banksia Hill Detention Centre, and only in limited and prescribed circumstances by specially trained and authorised officers," they said.

"Restraints are used as a last resort to prevent a young person from injuring themselves or other people. They are removed as soon as the young person no longer poses a risk to themselves or others."

The spokesperson said sedatives are not used on young people at Banksia Hill.

"Members of the Department-wide Aboriginal Visitors Scheme continue to frequently visit Banksia Hill, making themselves available to detainees seeking support," they said.

"The Department is looking to recruit more Aboriginal Visitors to increase their access to Banksia Hill and other custodial sites.

"Under reforms at the centre, an Aboriginal Services Unit will provide services and cultural support to young people. It will be comprised of Aboriginal welfare officers, mental health workers and nurses. Eight of the positions at the unit are newly funded."

The spokesperson confirmed the Department would establish a temporary youth detention facility at Casuarina to relocate the cohort of about 20 detainees for up to one year.

"All the same services offered at Banksia Hill including medical, mental health, education and other support programs will also be delivered at the newly gazetted facility."

National Suicide Prevention and Trauma Recovery Project spokesperson Megan Krakouer said the punitive system needed to be replaced with restorative justice to change lives.

"It has to be experts who lead the way not boot-licking bureaucrats that the government wants to appoint to keep the silences going," she said.

"In my view and based on success, myself and Gerry Georgatos, prison reformist, and others like us, restorative justice approaches are imperative if the government is serious about authentic rehabilitation."