St Bernadette's has a good record of dealing with difficult children, says the head, Keith D'Cruz. No pupil has been expelled in his 10 years, despite a minority with what he describes as quite severe problems.
But the orderly behaviour of the seven to 11-year-olds inside the modern, two-storey building is achieved by dint of unceasing effort, an effort that has become progressively harder.
This is partly because the school is no longer an all-female institution whose girls required a good reference from the parish priest. But he believes there has also been an underlying change.
"The type of child we're getting now is quite, quite different. They're very much more streetwise and they lack motivation. They're at school because they have to come."
An increasing number, he says, display disturbance ranging from withdrawn neurosis through to aggressive disruption. He is currently coping with a child whose tantrums have involved hurling a chair.
It is at the same time harder to seek outside help. The process for referring children to St Thomas's Hospital has, for example, become more difficult, while the joint healtheducation therapeutic service in nearby Brixton may soon require a slice of his school budget.
There is, however, help in the form of A Place to Be, a new counselling service run by volunteers and currently assisting in some London schools, St Bernadette's among them. It sees 32 of the pupils, individually and in groups; according to Mr D'Cruz, it is invaluable. His deputy, Caroline McCahill, wishes this chance to talk to trained - or currently training - counsellors were open to all the children.
Without this help and without the tight regime of the school, Keith D'Cruz would not, he says, be able to "keep the lid on". Inside St Bernadette's they behave: outside is a different matter.
"The self-discipline is just not there. The school does try to provide a world of very clear boundaries and it's noticeable that, when it's removed, you have to keep pulling the children back because they can't appreciate the freedom. They're tempted to run wild. Here they know the rules."
There are profound economic problems in the area. Thirty per cent of the children are from families with no work. Thirty-five per cent have only one parent in the family. Fifty per cent are on free school meals. Sixty-three per cent of pupils are from an ethnic minority.
He believes that the problem goes beyond finance, however. "I think a lot of the parents are more concerned with material things. They think they're missing out on the good things in life and the children are a burden.
"They try to give the children a lot of material things; even ones from the poor families get new bikes. But they're not giving them the love they need."
There is, in theory, a parish able to offer help and some degree of community life; 98 per cent of the parents profess to be Catholic.
But in practice, attending Mass is unpopular, says Mr D'Cruz, and many of the children are unfamiliar with the words of common prayers.