‘By the way, Mr. Gatsby, I understand you’re an Oxford man.’
‘Not exactly.’
‘Oh, yes, I understand you went to Oxford.’
‘Yes – I went there.’
Pause. Then Tom’s voice, incredulous and insulting: ‘You must have gone there about the time Biloxi went to New Haven.’
Another pause. A waiter knocked and came in with crushed mint and ice but, the silence was unbroken by his ‘thank you.’ and the soft closing of the door. This tremendous detail was to be cleared up at last.
‘I told you I went there,’ said Gatsby.
‘I heard you, but I’d like to know when.’
‘It was in nineteen-nineteen, I only stayed five months. That’s why I can’t really call myself an Oxford man.’

F. Scott Fitzgerald

The Great Gatsby. Chapter 7, in this confrontation between Tom and Gatsby, Tom attacks his education and calls him out as not being an Oxford man. It shows Tom’s condescending attitude towards what he views as Gatsby’s lesser education and class.