Whenever the bell sounds at the end of one of Andrew England's lessons, his pupils thank him before leaving. It is his pupils' genuine desire to learn that has persuaded the 47-year-old head of chemistry to remain at Roedean girls' school in Brighton, since his arrival as a newly-qualified teacher 24 years ago.
Mr England graduated from Queens' College, Cambridge with a degree in natural sciences. He obtained his teacher-training qualification from Oxford University's department of education.
He did not make a deliberate decision to work in the private sector: he wanted to teach both sixth-form and younger pupils, and pound;6,390-a-term Roedean was the first school to offer a suitable post. But he is quick to list the advantages of working at a selective school.
"It's very civilised. You can leave your wallet on the desk," he said.
And with 10 per cent of pupils going on to Oxbridge, his own experience often comes in useful.
As a science teacher, he appreciates the value of new science labs and up-to-date equipment: "We have a very generous budget. You can carry out almost any experiment that it's legal to do."
When he began at Roedean the school paid staff the national state salary. It now offers 7 per cent above national rates, and Mr England receives pound;35,000 a year.