Dave Levin discovered the secret of his success through an unfortunate mistake. In 1992, he was an idealistic young member of the Teach for America scheme. Fresh out of Yale, with minimal training, he had been plunged into the harsh realities of an elementary school in a deprived area of Houston, and he was struggling.
One day, faced with a 5ft 10in class bully completely ignoring his call to sit down, Mr Levin lost his patience and committed a complete no-no. He manhandled the boy across the room and, running out of strength, lost his grip on the overgrown 11-year-old, who slammed back into his chair.
Mortified, Mr Levin decided to break another cardinal rule. Ignoring warnings of the dangers for young white teachers of a largely African- American neighbourhood, he visited the boy's home to apologise. He was welcomed by a grateful mother, pleased that he was the first teacher to show her the respect of coming to her home rather than summoning her to school.
Today home visits are a cornerstone of the influential Knowledge is Power Program (KIPP) schools Mr Levin founded two years later with fellow Teach for America recruit Mike Feinberg. He believes teachers need to reach pupils' and parents' hearts as well as their heads to stand a chance of helping those from disadvantaged backgrounds reach their full potential.
And that means "home visits, things like all of our teachers giving out their cellphone numbers so they are available 247".
In 16 years, KIPP has gone from a single middle school in Houston to 82 schools covering 19 of America's 20 biggest cities.
That success is now making waves in England. Last summer the Cabinet Office featured KIPP in a report about "the world's best public services". And in November, when the Conservatives said they wanted teachers to set up their own schools, it was the "phenomenally successful" KIPP they cited.
I meet Mr Levin in a tiny interview room off a corridor in KIPP Infinity, an 11-13 charter school rated the very best of New York City's 1,100 state funded schools in 2008. It is housed on the third storey of a large red- brick building that contains an embryonic KIPP high school and three conventional state schools.
The West Harlem setting, immediately behind an enormous high-rise slab of public housing, is stereotypically inner-city New York, with a liberal sprinkling of graffiti tags on its lower levels.
But KIPP Infinity is an oasis of calm and order. To visit the "teachers' bathroom" you go downstairs to a floor occupied by a conventional state school where pupils hang around the corridors and you notice an instant rise in noise. Back in the KIPP sanctuary, the corridors, brightly decorated with slogans like `Climb the mountain to college' and `Infinity. No shortcuts. No limits', are empty during lessons.
At change-over time pupils, wearing T-shirts printed with the year they will graduate from university, line up and recite multiplication tables before entering classrooms decorated with pennants from their teacher's alma mater.
They are tactics known to anyone familiar with the US charter school movement. But non-profit KIPP was in at the beginning of this new culture of high expectations for disadvantaged pupils.
"We were starting with fifth graders, which are nine year-olds," Dave Levin remembers. "The idea we were going to talk to them about college, going to college and graduating college; no one was doing that. Everyone was talking about `let's do a little bit better on our state test scores'. We were talking about a transformative life change.
"That's the ultimate result. But you can't wait 12 years. You can't tell parents `Trust me, 12 years from now everything is going to be OK.' There has to be a focus on short-term results as well."
KIPP has succeeded on both counts with pupils who are 80 per cent low income and 90 per cent African American or Latino. After four years at its middle schools, all of KIPP eighth grade classes have outperformed their district averages in maths and English.
Even more importantly, 85 per cent of KIPP pupils go to university, compared with 20 per cent of low-income pupils nationally. The KIPP approach, which includes a relentless data-driven focus on test performance and accountability, is now succeeding in 19 separate states and in the District of Columbia.
Mr Levin does not have a big office or a personal assistant. The curly haired 40-year-old's collar and tie peek out under a crew-neck sweatshirt, making him look like a scruffy sixth former.
He shares the enthusiasm, and a touch of the geekiness, of those other two American pioneers, Apple's Steve Jobs and Microsoft's Bill Gates. Ideas come tumbling out at such a rate that he rarely has time to end a sentence. But you quickly grasp the energy and engagement that make him such a good teacher.
"How do you read that?" he exclaims when he spots I am using shorthand. "You have shorthand for numbers too? That's fascinating!"
Asked what a government would need to do to replicate the success of an organisation like KIPP in England, he answers: "Three Fs, and people. Funding, facilities, freedom. Then you need a systematic approach to how you find great people - principals and teachers."
It sounds neat. But apart from autonomy - which is a given in English schools, compared to those in the US - it is really a statement of the blindingly obvious. Of course schools need money, buildings and teachers to succeed.
A lot of what KIPP has done is breathtakingly simple. Mr Levin, for example, sums up a key factor in two words: "You need more time. Not just for the kids who struggle; you need more time for everybody. They go in 7.30(am)-5(pm), (do) two hours of homework, come to school on Saturdays and go to school for a month in summer - more time."
But KIPP's triumph has not been about easy formulas. In his US bestseller Work Hard. Be Nice, Washington Post journalist Jay Mathews relates how Mr Levin and Mr Feinberg succeeded through passion, grit and sheer bloody- mindedness, often stumbling across solutions on the way.
Harriett Ball, a colleague at Mr Levin's first school in Houston, showed them how important it was to make learning attractive for pupils, teaching multiplication tables through catchy, streetwise chants, a technique they dubbed "rolling the numbers".
Mr Levin sees that kind of approach as vital. "We have to compete today with all of the other influences in a kid's life - mass media, TV, movies, sports, music," he explains. "So schools have to understand that you have to be relevant. You have to make school cool; there is just no other way round it."
It is a lesson he passes on to other KIPP teachers. But KIPP's structure means there is no prescribed way of doing things. It does not operate like a chain in the way they are usually understood, rolling out a series of identical franchises.
KIPP selects its principals carefully - only 4 per cent of applicants are successful. They receive a year's training and then have to build their own schools from scratch - finding premises, hiring staff, establishing a culture, going through the same challenges as Mr Levin and Mr Feinberg faced.
They are supported by KIPP, and a menu of two or three proven curriculum approaches is being developed for them.
But Mr Levin stresses: "If they wanted to try something totally new they would still have the freedom to do that so long as it is tied to results."
Some believe that KIPP could be simply making poverty more palatable while leaving the really hard cases to conventional state schools. They cite evidence suggesting the programme attracts the more able and motivated pupils from poor communities and that test scores are inflated because the toughest pupils drop out.
"Parents and kids have got to choose the school for the most part," Mr Levin says. "This doesn't mean that you are creaming kids. We have kids across the entire bell curve of academics (ability) as well as motivation."
But he immediately seems to contradict himself: "If you are going to sign up you have at least got to want to do the hours. You can't have some kids go 7.30 to 5 and some kids go 9 to 3."
So what can be done for children who are not motivated enough to come in early?
"Hmmm. we really have not met many, especially as we become more established and more successful. People want to belong to something great."
But what about those whose parents don't buy into the idea?
"It goes back to that point about reaching to the heart. When you do home visits, give out cellphone numbers, when you are accessible for people, it is easy to build relationships. People want to believe."
KIPP achieves so much with the disadvantaged pupils it does attract that many would forgive Mr Levin for admitting there were some families beyond his help. But he won't.
"So many schools have problems with their parents," he says. "But you have got to ask what is the school offering that really is going to engage the families? And when you offer a bunch of things that parents want - they want their kids to learn, be safe and enjoy school, and they want to be treated with respect. When those things happen, parents are supportive.
"In 15 years and thousands and thousands of families, every single parent I have ever met wants what's best for their kid. There are families you have to work harder to build relationships with. And that's what great schools do. They don't accept the first response."
So there are no unreachable families?
There is a long pause. "There are no unreachable families."