All four are facing serious charges, accused of working with each other to defraud the Logan-based Kimberley College of significant sums of money between 2012 and 2018.
They were arrested at a home in the Logan suburb of Carbrook on Tuesday, with three of them to appear in the Brisbane Magistrates Court later in the day.
The Department of Education alerted police to serious concerns about the facility in August last year, sparking a high-level investigation involving the Major Fraud Investigation Unit.
"It was a complex investigation and involved the detailed and lengthy analysis of financial documentation and banking records," Detective Acting Superintendent Vince Byrnes said on Tuesday.
"The nature of the alleged offending is very concerning as it involves persons who were then acting in a position of trust."
The investigation sparked raids in July and August this year that resulted in the seizure of documents, computers and mobile phones from various homes in the Logan area.
A 35-year-old has been charged with fraud, dishonestly causing detriment as an employee where the detriment is greater than $100,000, perjury, and computer hacking.
She has been conjointly charged with a 34-year-old man on another count of fraud, dishonestly gaining benefit or advantage as an employee where the yield is greater than $100,000.
A 75-year-old man has also been charged with fraud, dishonestly causing detriment as an employee where the detriment is greater than $100,000.
He's been conjointly charged with the 35-year-old woman for one charge of extortion and computer hacking relating to a separate complaint made to police in 2016.
In addition, the 75-year-old has been conjointly charged with the 34-year-old man with one count of fraud, dishonest application of property of another greater than $100,000.
A 66-year-old woman is also facing a charge of fraud, dishonestly causing a detriment as an employee where the detriment is greater than $100,000.
The 75-year-old man has also been conjointly charged with the 66-year-old woman on one count of fraud, dishonestly gaining benefit or advantage as an employee where the yield is greater than $100,000.
The two men will face court on Tuesday, along with the 35-year-old woman.
The 66-year-old woman has been issued with a notice to appear in court in coming weeks.
The co-educational independent school has nearly 1000 students enrolled from prep to year 12.