An 11-year-old boy, described by a West Australian magistrate as the "state's most vulnerable child", has avoided penalty for 36 criminal charges.

The boy, who the ABC cannot legally name, spent a total of 77 days in Perth's under-fire Banksia Hill Detention Centre but was released from custody after his court matter concluded.

Court transcripts, obtained by the ABC, outline the boy's criminal trial in the Perth Children's Court, which finished on October 8.

The boy's charges included 16 counts of aggravated burglaries, as well as stealing a motor vehicle and assault occasioning bodily harm.

State prosecutor Taylor McAnderson submitted there was a need to implement wraparound services to prevent the boy from reoffending.

The court also heard the 11-year-old was currently in the care of the Department of Communities.

Magistrate Samantha Martella said the department needed to invest in the boy, educate his family and work with the education department to keep him out of trouble, regardless of resourcing restraints.

The court heard of the 77 days in custody at Banksia Hill, the longest consecutive stint was 19 days.

Time spent in custody considered

Defence lawyer Kerrigan Mercer said her ultimate submission was for no more punishment, given his total time spent in custody.

In court, 27 of the boy's charges were dismissed on "public interest grounds".

The magistrate then read the remaining nine charges to the boy, where guilty pleas were entered.

One offence included an incident where the boy was armed with a 10-centimetre blade outside a bar.

A youth justice officer confirmed the boy's time spent in custody, which Magistrate Martella cited as a reason to pass no punishment.

Magistrate Martella also said there had been a gap in the boy's offending.

A caseworker, whose identity was redacted by the court, told Magistrate Martella the child had the "highest level" of complex care arrangement due to trauma.

They said the department was awaiting approval for formal assessments, of which ADHD and Foetal Alcohol Spectrum Disorder were flagged.

The caseworker said the state continued to work with the boy's mother, in the hope of him rejoining his family in northern Western Australia.

The court heard the boy had previously been in a "family-type care arrangement" with siblings, but the caseworker said the department's resources and staffing model could not "meet his needs" and the offending then increased.

The caseworker also said they have planned for the boy to eventually return to school.

"We've got a plan to reintegrate him into mainstream schooling," they said.

Sentencing considerations

The state prosecutor, Ms McAnderson, said concerns had been raised over a lack of consequences for the boy, which was believed to have led to his reoffending.

However, Magistrate Martella said his consequential thinking may develop later given the boy's age and potential diagnoses.

The magistrate also highlighted the state government's need to provide more support.

"It's the state talking to the state," Magistrate Martella said.

While Ms McAnderson agreed with the magistrate's comments about the state's responsibilities, she raised concerns about the seriousness of the boy's offending.

"There is an element of community protection when it comes to this sentencing exercise, given those offences," she said.

Magistrate Martella said investment in the boy's support network and therapeutic needs would be "paramount" in the weeks ahead.

The magistrate told the boy that court was not a place for young people and that she did not want to see him again.

She asked the boy if he understood what he needed to do.

He replied: "Yes — stay out of trouble."