Five years ago Stockwell Park High School notched up almost 300 fixed-term exclusions per year.
The school emphasises its high expectations
Fighting and bullying were the most significant factor, according to deputy head teacher Devon Hanson.
It was a failing school - just 11% of pupils achieved five GCSEs at grades A-C or the equivalent.
Three quarters of children are entitled to free school meals. Some face issues such as overcrowded living arrangements or disruption and trauma at home.
The school came out of special measures in 2001, and last year 58% achieved five good GCSEs or more. It has reduced its fixed-term exclusion rate to around 20 per year.
It focused intensively on stopping children fighting, bullying and disrupting lessons - and on raising standards.
"We now have better systems and structures to prevent the situation getting to a fight," Mr Hanson said.
"We have instilled confidence in the children that we will deal with any matters which arise."
As head of pastoral care, he is a visible presence around the school, particularly between lessons.
Thirty members of staff, including all senior managers, carry a walkie talkie, alerting them quickly to any kind of problem.
"They improve our rapid response and keep us in tune with what is happening in the school," Mr Hanson said.
He is in no doubt that teachers need to be supported when sanctions are necessary.
"We as teachers are in loco parentis. I would question any teacher who did not intervene to stop a fight."
Senior management are available to pupils and parents
"If there has been a serious altercation in class, we never have that child in that same class the next day - it sends the wrong message."
The school acts as a "community within a community", Mr Hanson said.
A strong house system with a competitive edge helps build that environment.
Motivational assemblies include everyone and celebrate achievement.
Treating children "like they can, rather than can't" has seen them change their attitude in return, Mr Hanson says.
Every new year seven pupil is interviewed "to make that child feel as if they are wanted here".
"And we make it clear to parents that this is a partnership, and we cannot educate their children alone."
Parents sign a declaration that they have read and understood what constitutes unacceptable behaviour.
The school says it asks children to give their best, and in return it gives them the support they need to do so.
Any child who has a problem studying at home can stay in school until 1900 or come in on Saturdays.
There are regular free residential courses, and parents are encouraged to visit the school to discuss concerns.
Among other initiatives aimed at fostering a community spirit and celebrate achievement are mentoring by older pupils, an academy system which rewards success with bursaries, and leadership programmes for children.
"The words 'can't do' aren't spoken much in this school," Mr Hanson went on. "We talk about opportunities."
The motto "Attitude determines altitude", borrowed from Nasa, is displayed all around the front entrance and assembly hall.
Marketing and PR consultant Kerry Staveley said the school is in the process of applying for government "building for the future" funding.
The 1970s facilities are "in need of repair", she said, and it has no sports facilities.
Ms Staveley's job is to raise the profile of the school in the local community and capitalise on its recently-acquired business and enterprise special status.
"A few years ago kids didn't want to come here and parents didn't want to send their children here," she said.
"The community looks on us as a positive thing now."
She is encouraging businesses to work with the school to help teach children the skills they will need in the world of work.
"We consulted pupils and they came up with skills such as teamwork and self-analysis. They learn the skills they need to be successful."
"The pupils have taken on a much more positive attitude, and it's exciting working here," she went on.
"And we make a big thing out of publicising our success."
A large, diverse body of secondary school pupils are typically boisterous at lesson changeover. But the atmosphere is a good-natured one.
There are pupils of all ethnic backgrounds at the school.
But, Mr Hanson tells me: "We don't talk about race. Race is not a problem. We don't talk about 'Black history month', we talk about 'world history month'.
"I tell the children they are history. What is the history they want to leave behind here - a trail of under-achievement? Or will they know they are the best they can be?"