Summer schools for England's brightest children have improved in quality, with all providing good or excellent teaching, a study says.
Academy students get to try new subjects, such as ecology
The education watchdog Ofsted found courses run by the National Academy for Gifted and Talented Youth had also been fully subscribed in 2004.
Only 500 out of 900 available places were filled the previous year.
The summer schools give 11 to 16-year-olds the chance to try new subjects like astronomy and ecology.
Students are drawn from among the 5% brightest of their age groups.
During two- or three-week residential courses they are exposed to university-level tuition in an effort to stretch them further and broaden their academic interests.
They can learn new subjects, like film or cultural studies, or take advanced courses in familiar subjects like English and maths.
Each academy place costs £1,900, with most parents expected to contribute.
However, funding arrangements meant children "were recruited from a wide range of socio-economic backgrounds", Ofsted said.
Academic progress could be improved further in some centres by teaching pupils in narrower age groups, as there were "limitations" in grouping the whole 11 to 16 age range together.
There were also "marked gender differences" for some subjects. Some 90% of pupils on a robotics course were boys, while girls outnumbered boys in English.
Ofsted found children's welfare was dealt with well, but, although teaching had improved since the first summer schools - in 2003 - some was still "over-directed".
The academy needed more information on pupils' previous school performances to tailor courses to their needs.
The academy's director, Professor Deborah Eyre, said students were being offered "an outstanding, often life-changing, opportunity".
Schools minister Stephen Twigg added: "The fact that twice as many gifted and talented youngsters attended schools last year is indicative of the success and popularity of the programme."
The summer schools are run at universities in Canterbury, Durham, Exeter, Warwick, York, London and Lancaster.
Almost 1,050 children attended last year.
The Ofsted report is called National Academy for Gifted and Talented Youth: summer schools 2004.