As she sits down, breathless, the assembled grown-ups applaud. In their midst is Dr Bindeshwar Pathak, a man in cream Nehru jacket, shirt and loose trousers.This school - the first English-medium school for scavengers in India - is his brainchild.
Scavengers - or bhangis - come from the harijan, previously Untouchable, caste. Euphemistically called sweepers, they are the midden-men and women, who clean pit toilets, either with their bare hands or small shovels, and carry away the raw sewage in buckets or large metal trays on their heads.
In pre-Gandhi days, they were ostracised and made to wear bells round their necks to warn people of their approach. Even today, they remain the lowest of the low - other Untouchables, like animal cremators and tanners, avoid them. India has about 500,000 scavengers - a nation where only 230 towns out of 5,000 have a proper sewerage system.
Low-cost sanitation - which would abolish the need for scavengers - is an abiding passion for Dr Pathak, who 25 years ago launched Sulabh International. At its Delhi headquarters, sanitation technicians develop flexible and affordable technology to suit the needs of different towns and villages - a grass-sided toilet for one, bricks for another. To date there are about 3,000 Sulabh complexes throughout the country. (The headquarters include a health centre set in landscaped gardens which flourish thanks to human manure. There's even a toilet museum, with exhibits from more than 60 countries and covering 5,000 years, including a replica of the toilet Louis XIII of France sat on during audiences.)
And down an unmade lane by the side of the complex is the Sulabh Public School. It's a single-storey building with bright alphabet murals on its whitewashed walls arranged round a garden and playground. In the middle is a statue of Dr B R Ambedkar, the Indian freedom fighter who himself came from one of the scheduled (low) castes.
The school was built five years ago to educate scavenger children out of the family profession. "We want them to acquire the skills and education to go out and become good citizens of India, " says headteacher Sheel Kasab."Ninety-five per cent of their parents are illiterate, so everything is on our head. They [the parents] can't speak English, some don't even know proper Hindi. They're very happy to see their children being educated. They want to make them sahibs - officers, doctors, police officers, engineers. Even the children have the spirit and ambition to become these things. "
In the first year, all the children came from scavenger families, but to ensure they are not ghettoised, 40 per cent are now non-scavenger. Ages range from four to 13. As is usual in Indian schools, they learn through songs, rhymes, even hymns and by rote.
In one room, children are chanting, "Early to bed, early to rise#201;" In another, they are block printing, and drawing pictures of rats and sunflowers. There's a classroom for disabled children. In the afternoons, 85 street children arrive to learn Hindi, English, maths and general knowledge.
There is also six-month on-site vocational training for 16 to 25-year-olds from other schools, half from scavenger families. They are taught hand and machine embroidery, beauty therapy, typing in English and Hindi, cutting and tailoring, and computer technology. All the courses are recognised and examined by the Indian Training Institute.
Why English-medium? "English is the language of business," says Mrs Kasab."We want them to be able to compete as equals in the open job market."
The school is consistently oversubscribed - 400 applications for the annual 40 places. Staff check the families' original caste certificates, ensure they live within 10km of the school and give preference to siblings.
"The main thing is to take a child from a poor background. The poorest among the poor," says Mrs Kasab. For scavenger children, everything is free - education, uniforms (one for winter, one for summer), shoes, books, excursions, transport, a midday meal of fruit - costing the school 1,500 rupees per child a month (#163;30). Non-scavenger children pay a nominal fee of around #163;2 a month.
The teachers know they could earn more and work shorter hours in the state schools, but they are committed to the Sulabh cause. "We feel we're doing something for the poor," says Mrs Kasab. "That feeling is in our heart."
Mrs Vimla Devi, an illiterate sweeper like her husband, has three children at Sulabh. "It's nice to be educated," she says. "They'll get good jobs. I want my daughter, who's 12, to be a doctor. I won't be happy if they're sweepers.