The latest independent schools' census showed that increases in fees may have contributed to the end of the boom.
The number of pupils at 1,267 fee-charging schools in the UK rose 0.1 per cent to 505,342, up from 504,926 in 2003, the Independent Schools Council (ISC) said.
It was the ninth successive year of growth, a record for the sector. But the 0.1 per cent rise followed a 1 per cent increase last year and was the smallest since 1996, when private schools began to expand again after contracting during the recession of the early 1990s.
The number of pupils from other countries rose 3.3 per cent this year, including an 11.2 per cent increase in the numbers coming from Germany.
School fees, jumped 9.6 per cent to average pound;3,074 a term. Boarding fees were up 9.1 per cent to pound;5,909, while termly rates at all-day schools rose 10.1 per cent to pound;2,429.
Day-only pupils at boarding schools saw average fees rise 9.1 per cent to pound;3,107, giving an average termly day fee of pound;2,637, an increase of 9.7 per cent on 2003.
The Office of Fair Trading last year launched an investigation into allegations that leading private schools exchanged information about provisional fees before deciding on charges. The ISC has advised schools not to exchange financial information in case they fall foul of competition law.