One in eight children in Cardiff now receives a Welsh-medium education and in Powys more than 50 per cent do so.
The percentage of children receiving Welsh-medium education in Cardiff will rise to 12 per cent this autumn with the greatest number ever choosing places in Welsh-medium schools.
Tim Pearce, of RhAG (Parents for Welsh Medium Education), said: "Every time a Welsh-medium school opens there is a flood of parents wanting their children to go to that school.
"The numbers are snowballing and I think it is partly because, in recent years, there has been more emphasis on Welsh identity, especially with the creation of the Welsh Assembly.
"Sixty per cent of the world is bilingual and research has found it improves mental agility and makes learning other languages easier.
"Teachers are thought to be more committed in Welsh-medium schools as they are seen as having a missionary zeal which parents appreciate.
"Welsh-speaking schools also espouse more traditional values which parents like."
RhAG claims it is constantly battling with local authorities to establish more Welsh-speaking schools and has criticised them for dragging their heels on the issue.
There are 444 Welsh-medium primary schools and 50 Welsh-medium secondary schools in Wales.