GLADSTONE Police and Child Protection officers have interviewed students from Toolooa State High School over a series of graphic mobile phone photos.
Staff at the school seized phones from a group of Year 8 students on Friday after they became aware of the explicit images.
A spokesman for the Education Department would not confirm the number of students involved.
"The principal of Toolooa State High School became aware of an issue occurring off school grounds involving a number of students," he said.
"As a result, both the school-based police officer and the Child Protection Investigation Unit were called to the school."
One concerned parent said 20 girls, aged 12 and 13, were interviewed at Gladstone Police Station on Saturday.
He believed they all sent graphic "selfies" to a male student, also in Year 8.
It's believed the sexting took place in April and May, and it's unclear what prompted the discovery.
The families do not know how widely the images, sent via the Kik app, have been circulated.
One father told The Observer he'd felt like "his head had been blown off" by the revelations.
"It's normal for parents to think their children are innocent, and wouldn't do anything like that," he said. "But it seems it's the world we live in.
"Technology opens up doors that we would never have thought of when we were children."
In the first five months of this year, Queensland Police charged 240 under-18s with producing and distributing child pornography.
Most of the charges were attributed to the growing trend of sexting.
The Toolooa dad said police had assured him no convictions would be recorded against the girls.
But police confirmed investigations were ongoing, and the school was assisting.
Toolooa will not undertake disciplinary action while the investigation is underway.
And the father said his daughter wouldn't get her phone back for "some years".