Observers of the American school system might remember a “hero figure” from the 1980s - one Joe Clark, a principal who “transformed” a high school in Paterson, New Jersey. Mr Clark was the subject of a cover story in Time magazine. He produced a phenomenal rise in test results and the school became over-subscribed. So what was the secret of his success? He expelled more than three hundred pupils who he described as “parasites” and “leeches”.

So now we have Dave Levin who has “discovered the secret of success” with the Knowledge is Power Program (KIPP) schools (“Meet the man who believes pupils should have your mobile number,” February 19). The truth is that potential parents are rigorously interviewed. They are then required to sign a contract allowing their children to attend school from 7.30am to 5pm and agreeing to monitor two hours of homework every night. Saturday school is compulsory, as is one month’s school attendance during the summer holidays.

There is, predictably, a high turnover rate - in some KIPP schools nearly 50 per cent of pupils don’t make it to the eighth grade. Another feature is teacher “burn-out” - not surprising when the standard working week is 65 hours and you are expected to be in contact by mobile phone 247.

In some American cities more than half of pupils are either educated privately or at charter schools. The state schools are then left with pupils of lower academic ability and a much higher percentage of parents who do not support their children in school.

Why doesn’t the US look to Finland as a source of inspiration? Ninety-nine per cent of Finnish children attend the local state school, where uniforms are banned, they don’t test children to death (a feature of KIPP schools) and league tables are non-existent.

Richard Knights, Liverpool.