Summer schools for gifted children at five universities are struggling to recruit because parents say their residential courses are too long.
The National Academy for Gifted and Talented Youth has so far filled only 255 of 900 places on the three-week summer schools at Warwick, Exeter, York, Durham and Canterbury universities.
The academy, based at Warwick, has extended the deadline for entries to the schools until the end of July in an attempt to attract more applicants.
But Warwick spokesman Peter Dunn admitted it was "unlikely" that the schools would come close to being filled.
He said: "The one common complaint we seem to be getting is that three weeks is too long for a residential school. The parents seem to think this is too long to let their children go."
He added that the lower numbers would make no difference to the way the courses were run.
The academy was launched by school standards minister David Miliband last year. It was based on a scheme run at Johns Hopkins University in the US and was designed to raise aspirations and open opportunities for gifted children from all backgrounds.
The cost of courses for children from poorer backgrounds is subsidised by the government and schools.
Mr Dunn said that with 1,100 members and 100 joining each week, the academy was on track to achieve its target of 6,200 members by September next year.
Children must submit evidence through their schools that they are among the country's 5 per cent brightest before they can become members.