The Swan School of English, one of Oxford's oldest private language colleges, is to close after 40 years with the loss of more than 20 jobs.
The owner of the Banbury Road business, H A Swan, said: "We have had a bad couple of years financially and we didn't really see a future for private language schools."
Mrs Swan said the decision had been taken after much heart-searching, because of increasing competition from the state sector.
She added: "I'm really upset at having to close because it's my life's work. But I wanted to take a responsible decision, so that I can pay staff and not let down any students."
Mrs Swan, 65, is known as H A and her real name is a closely-guarded secret. She set up the school at the age of 25 with her then husband Michael Swan, who wrote Practical English Usage, How English Works, the grammar bible for English learners.
Many other Swan staff have written best-selling textbooks and the school pioneered interactive ways of language teaching.
She said: "We started with the vision of providing a unique learning experience for all our students, very high-quality teaching and a place where staff could thrive and develop. We feel we have managed to achieve this.
"However, the pressure to change - and not, we feel, for the better - has become too strong. We would like the Swan School to be remembered for what it has achieved and are not prepared to compromise the school's high standards."
Meanwhile, another Oxford language school owner, Till Ginns, has just completed a takeover making the Oxford Intensive School of English (OISE) the largest English language group in the UK.
The takeover of seven UK Regent schools means OISE now owns more than 20 schools worldwide, with £27m turnover and 25,000 students. It also runs 20 summer schools.
Mr Ginns started OISE in 1973 in Jericho, to help fund his philosophy doctorate.
Mr Ginns said: "In the private language school world, it is not just education that counts -- it needs to be commercially-driven. If it is well run as a business, it can achieve both aims successfully."
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