Bill Gates is donating more than $40 million (pound;28m) to cut the spiralling class sizes blamed for soaring student dropout rates.

The grant, from the software mogul’s Bill and Melinda Gates Foundation, will help establish 70 secondary schools with no more than 400 pupils.

The schools, across the US, will offer accelerated learning enabling students to enter university with credit towards degrees.

The initiative is targeted at racial minority and poor students, who will most gain from closer supervision and intensive instruction. Some 55 per cent of black and Hispanic pupils quit school early, compared to a quarter of other students.

American high schools, which cater for 13 to 18-year-olds, have doubled in size over the past generation leading to “anonymity and incoherence”, said Tom Vander Ark, the foundation’s executive director of education.

The nation is doing poorly in the international education league: maths and science students are two years behind their peers in other industrialised countries.

Raising standards and reducing school size go hand in hand, says Mr Vander Ark. “Students need to be on rigorous courses, but you can’t engage all students without personalising education.”

However, while fast-track learning has worked with gifted children, Mr Vander Ark conceded that extending it to less able pupils, and expecting them to study university courses while completing their high school diploma in as little as four years, was ambitious.

Nevertheless, he said, the project would tap the experience of participants like the Middle College high school consortium, which runs hothouse schools on college campuses. Smaller schools have proliferated in New York, Chicago and Boston in recent years.

New York’s Urban Academy sends 97 per cent of its 120 deprived students to college. The state school draws its intake - two-thirds black or Hispanic - from those struggling at larger schools. “No one falls through the cracks,” said co-director Ann Cook.

Gates and other donors will pay some $50m for the schools to open their doors. But after that they are on their own. Leon Botstein, president of Bard high school early college, a small accelerated learning school near New York, called for funding to sustain it. “It’s not an idea that should be ruined by being tried without (proper) backing ,” he said. Most of the schools are expected to open in 2003 or 2004.