The brothers have pledged $1 million to the MAGS Foundation, which will use half to invest in a new Centenary Endowment Fund.
The foundation, a charitable trust independent of the decile 7 school, wants to build the fund to a target of $10 million by the time MAGS celebrates its centenary in 2022.
The plan is to use its interest and proceeds to perpetually fund initiatives such as student and staff scholarships and improvements to infrastructure.
"There is a general awareness at state schools that want to make progress that they will have to look at this type of model," said headmaster Dale Burden.
Chris Liddell, who flew back to New York last night, said the Government was the primary funder of state education but support from private citizens was important. The former MAGS dux hoped other former students would give to the fund, no matter how small the contribution.
It was right for education to be front and centre as an election issue, he said.
"It's probably more important than it's ever been, with some of the forces that we see in the world, particularly technology and how that's changing the shape of people's jobs."
About half of the $1 million donation will be used to continue existing Liddell Scholarships for students and highly performing teachers.
The brothers' father was a teacher, and they said it was important to recognise the crucial role school staff held.
John Liddell remembered entering headmaster Maurice Hall's office after their father died suddenly of a heart attack to say he was quitting school to work as rubbish collector.
"He said, 'No, you can't do that.' ... he said come to school when you can. So I think I was the only boy who was allowed to come and go from school when he wanted.
"That was the kind of approach the school took, and I've never forgottenit. And Maurice Hall was quite right - it stayswith you for the restof your life when you're supported."
