A free school headteacher has warned that recently qualified teachers can “hop off the bus” into independent education where they can earn more after they have been trained.

Clare Wagner, the head of West London Free School, said that the state system was losing trained teachers to private schools and said raising state school teachers’ pay was vital.

Ms Wagner was speaking at a fringe meeting on the future of education funding at the Conservative Party conference.

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She told the audience that she had worked in both the state and private sectors.

Ms Wagner said: “Increasing teachers’ pay for recruitment and retention is vital. The future of our children’s education lies in the quality of the teachers that stand in front of them every day. 

“In the private sector, the calibre of the candidates we got was exceptional: firsts, 2:1s from top universities.

“I am really lucky at my school, I have exceptionally well-qualified teachers from Oxford, Cambridge, privately educated - they really believe in the school and they really believe in what they are doing.

“But the reality is I also pay to train lots and lots of NQTs, as do my other colleagues in the state sector, and many of them after we have trained them are going to hop off the bus, to go into the private sector where they immediately get a £10,000 pay rise. They get longer holidays, and they get less contact time.

“I want to keep the best in front of my pupils. It’s the only way. You have to have brilliant, inspiring, passionate teachers.”

She also called for more post-16 funding for schools, warning it was affecting the choice of subjects open to pupils in the state sector.

She added: “I get more money for my key stage 3 and 4 pupils than I do for my sixth-formers. I do not understand that at all.  We are not investing in our 16- to 18-year-olds.

“In my sixth form, I have these huge, huge classes who want to learn maths and biology. I have had to cut some subjects at A level because I simply can’t afford to teach some of the subjects I would love to.”

The National Education Union and the Conservative Education Society held a fringe meeting into the future of education funding today.

John Bald, the chairman of the Conservative Education Society, said that most Conservatives accepted that funding cuts had gone further than what was necessary for austerity.

Kevin Courtney, the joint general secretary of the National Education Union said the Conservative Party had made good steps on school funding but added that the amount the government has announced was not enough.

He said that analysis from the School Cuts coalition had found that 80 per cent of schools will still be funded less well than they were in 2015.

Teacher Steve Mastin said that increases in school funding should be targeted at areas that have historically received less per pupil.