Katherine Birbalsingh, who has earned a reputation as "Britain's strictest head", has launched a scathing attack on the Oxford Union.
The Headteacher at Michaela School in Wembley wrote a letter to the Union, accusing them of cancelling a debate she was asked to attend.
The outspoken educator accused students of showing "rudeness" and being "ill-mannered".
In a public letter addressed to the President of the Oxford Union, Ms Birbalsingh slammed the behaviour of the group.
She told GB News: "When you just think of what the Oxford Union used to be, it was so revered and so admired... it was just such a different place, really. And now it's just, it's so embarrassing.
"They're just political activists who have hijacked the union in order to fulfil their own desires. And they're certainly not interested in critical thinking or in hearing anything that would slightly offend them."
The Oxford Union is the world's most prestigious student-led debating society, founded in 1823 to uphold free speech at the University of Oxford.
It operates independently of the university, hosting weekly debates on current affairs, hosting prominent global speakers, and providing members with libraries and social spaces.
Katharine Birbalsingh has been branded 'Britain's Strictest Headteacher' | GETTY
Her letter read: "As a Headmistress and education reformer, I take a great interest in the future generations of this country.
"Sometimes I despair, knowing that what we are teaching children in schools, combined with our increasing general culture of complacency, victimhood and arrogance, will result in young adults who are not able to lead honourable and dignified lives.
"I am afraid that your own recent behaviour as well as that of your colleagues, only serves to confirm this worry of mine.
"You wrote a very nice and what read like a personal letter in March, inviting me to speak at the Oxford Union, to take part in the debate, 'This House Believes that Being British is a Birthright, not a Choice'. I agreed to take part, naming my preferred date. Your assistant Mr Yan wrote to say how excited you all were at having me with you.
"My PA wrote a subsequent four times as well as calling the Union, to enquire as to what was taking so long in finding a date that might work for everyone."
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Oxford Union has a reputation of a prestigious debating society
| GETTYShe continued: "We never received any more communication from the SIX people in that email, you, your assistant, the treasurer, the librarian and two others. I don't understand the rudeness demonstrated towards my PA.
"Stonewalling is never a good look. At the very least, you might have written and explained that you had changed your mind. How can it be that six young people in positions of authority at the Oxford Union can be so ill-mannered?
"Having now observed online that you chose to rescind your invitation to Carl Benjamin, who would have been on the opposing side to me in the debate, I see that at the very least, your rudeness is widespread.
"That's the thing about life, you see: you will come across people whose views you do not like. Carl and I may disagree, but I believe in treating him with decency and respect nonetheless. This is the nature of the adult world."
The Headteacher at Michaela School in Wembley wrote a letter to the Union, accusing them of cancelling a debate she was asked to attend
| GB NEWSMs Birbalsingh added: "However, I suspect that you and your colleagues are so convinced of your righteousness and moral superiority that you feel justified in treating two of your invitees, on either side of the podium, so appallingly.
"One can only achieve a life of honour and dignity if one is open to hearing from those with whom we disagree.
"This is because all people are flawed and so all must be curious as to what they can learn from those who think differently.
"Such openness and curiosity is a foundational pillar of Western civilisation. The education system has clearly let all of you down."
The Oxford Union has been contacted for a comment.