She claimed that the school taught about racism and sexism while insufficient time was dedicated to teaching reading and writing, and that children from disadvantaged backgrounds were let down.
Resident claims Leeds pub music is 'like a bad night in Benidorm’ amid plans to extend opening hours
17 pictures you'll only understand if you're from Leeds
Bus services refuse to go through parts of east Leeds due to ‘antisocial behaviour and vandalism’
Outpouring of love for Leeds pub compared to 'bad night in Benidorm' by resident opposed to extended hours
Aberford Road crash leaves man with injuries believed to be 'potentially life-changing'
At her Conservative Party leadership campaign launch today, she said: "Many of the children I was at school with were let down by low expectations, poor educational standards and a lack of opportunity.
"Too much talent went to waste."
The school falls within Mr Hamilton's constituency and he has lauded it as an "excellent educational institution".
He tweeted: "Once again, Liz Truss has shown she knows little about North East Leeds. First, she wrongly suggested that Roundhay was a red wall seat and now she has criticised our hard working teachers and school staff in Leeds.
"Roundhay School has been an excellent educational institution for decades and its staff and students are real assets to our community. It’s shameful that Liz Truss has decided to attack them today."
Speaking about her education at Roundhay School in 2020, Ms Truss said: "As a comprehensive school student in Leeds in the 1980s and 1990s, I was struck by the lip service that was paid to equality by the City Council while children from disadvantaged backgrounds were let down.
"Rather than promote policies that would have been a game changer for the disenfranchised like better education and business opportunities, there was a preference for symbolic gestures."
Ms Truss was born in Oxford but her family moved to Scotland and then on to Leeds, enrolling her at Roundhay School.
She came third in the first round of voting in the race for leadership of the Conservative Party, falling behind Rishi Sunak and Penny Mordaunt.