Two months later on May 27 at the Ballarat Law Courts, the 15-year-old boy started a fight with security staff over a cigarette lighter, spat on a police officer and racially abused him.

The teenager pleaded guilty by video link at a children's court on Wednesday to three counts of armed robbery, one count of burglary and one count of affray.

The court was told the teenager was involved in a burglary at a Sebastopol house and the three armed robberies at the water park within 24 hours on March 22 and 23.

During the offences the teenager wore a shark mask and motorcycle helmet to disguise himself.

The teenager requested the three victims remove some of their clothing and mobile phones, while his co-accused allegedly used a garden saw to threaten them.

Frightened, the victims did as they were told before they fled to nearby houses for help. The court was told police arrived later at the teenager's Sebastopol bungalow where the stolen items were located.

The affray at the Ballarat Law Courts foyer started after the teenager was asked to leave but he punched a security guard in the shoulder, spat at a police officer and racially abused him.

The teenager's lawyer urged the court to bail her client before sentencing to allow a youth justice group conference to occur.

But the magistrate said the public's safety could only be guaranteed if the teenager remained in custody, and he refused bail. His sentence was deferred for 10 weeks for a pre-sentence report and group conference to occur.