Knox teacher Wiliam Gulson arrives at   Downing Centre Court on Tuesday, 27 January 2026.  Gulson has been charged with child grooming.   Photo: Sam Mooy / The Sydney Morning Herald
A former school teacher’s excuses for graphic internet searches and a sexualised chat with a teen have been slammed as wholly unconvincing, as he was found guilty of a child sex offence.
William Roberto Gulson taught at Sydney’s elite Knox Grammar School and conducted private tutoring before he messaged a 15-year-old girl, posing as a boy, in August 2024.

In a recent case presented at Sydney’s Downing Centre Local Court, it was revealed that a teenage girl, alongside another adolescent, was operating a counterfeit profile on the LGBTQI dating app Grindr. Their aim was to expose individuals with predatory tendencies.

Knox teacher Wiliam Gulson arrives at   Downing Centre Court on Tuesday, 27 January 2026.  Gulson has been charged with child grooming.   Photo: Sam Mooy / The Sydney Morning Herald
Knox teacher Wiliam Gulson arrives at Downing Centre Court on Tuesday, 27 January 2026. Gulson has been charged with child grooming. Photo: Sam Mooy / The Sydney Morning Herald(Sam Mooy)

During the court proceedings, it was disclosed that a teacher responded to a photograph sent by the teenager with the compliment, “Such a cute boy.” This exchange was significant as it contradicted the teacher, Mr. Gulson’s assertion that he believed he was communicating with an adult.

The court heard that Gulson did not once refer to the person he was conversing with as an adult in their extensive conversation. Instead, he urged the supposed boy to leave his parents’ home secretly so they could rendezvous and find a “quiet place” for intimate activities.

Adding to the gravity of the situation, Gulson went on to describe in explicit terms the sexual acts he wished to engage in with the teenager. This revelation underscored the seriousness of the charges against him.

“Collectively, this is powerful evidence,” remarked Donnelly, highlighting the strength of the case built against Gulson based on the evidence presented.

“Collectively, this is powerful evidence,” Donnelly said.

Gulson, who faced a three-day hearing in September, remained impassive as the guilty verdict was handed down.

The offence carries a maximum penalty of 12 years behind bars.

His bail was continued ahead of his sentencing in March.

Gulson did not speak to reporters as he left the courthouse alongside his brother, who was at his side during the hearing.

The family of the teenager dialled into the courtroom to hear the outcome after being granted special permission.

1800 RESPECT (1800 737 732)

National Sexual Abuse and Redress Support Service 1800 211 028

Kids Helpline 1800 55 1800 (for people aged 5 to 25)

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