A government-backed summer school for bright children has filled fewer than one-third of its available places.
Applications to three-week courses are down on last year
The National Academy for Gifted and Talented Youth, based at Warwick University, is offering 900 pupils the chance to attend.
But only 255 places on its summer courses - for which it started charging for the first time this year - have been filled
The academy is now extending its applications deadline beyond next month.
Spokesman Peter Dunn said: "We hold up our hands. There are, I think two reasons for the shortfall.
"There was a bit of messing around over setting the fee. The government came up with more money, for which we were very grateful. But it delayed the applications process.
"It took a couple of months to apply for the extra money.
"More importantly, we are getting a lot of parents saying that our three-week residential courses are too long.
"We based ourselves on an American model. Over there, it's common for children to go away for long periods in the summer.
"Over here, perhaps people are not used to it. It's something we have to look into."
The summer school costs £600, with schools paying £270 and parents the rest.
It aims to give pupils from the top 5% of the 11 to 16 age group experience of subjects not often taught in normal schools, such as astronomy, Japanese and forensics.
The academy, backed by the Department for Education and Skills, is intended to reach 6,200 pupils by September next year.
As well as the summer school, it has started running one-off events, evening classes and one-day "master classes".
Mr Dunn said: "We are currently registering 100 new children a week and 1,100 have signed up as members.
"That seems to suggest we are on target to meet next year's target."
It is hoped up to 150,000 children will eventually take part in the academy's programmes.
However, John Dunford, general secretary of the Secondary Heads Association, has expressed concern over the creation of an "elite group" among pupils.
The academy began as a pilot scheme last summer, with 100 children taking part in summer courses after 520 applications - more than double those so far this year - were received.
It is expected to cost £20m over its first five years and will be supported by government funding, Warwick University, business and donations.