The number of under-16s is expected to fall
The Office of National Statistics (ONS) predicted on Thursday the number of under-16s would fall from 12.1m in 2000 to 11m by 2011.
The number of children in that age bracket is then expected to plateau for the next 15 years, the ONS reported.
The predictions came on the same day as official figures showed that hundreds of infants in England were being taught in classes of more than 30 pupils.
Assistant general secretary of the Secondary Heads Association, Bob Carstairs, said the drop could be the solution to teacher shortages.
"The drastic shortage of teachers would probably be alleviated but I don't know how that would impact on the number of schools," he said.
"It could well have some implications for redundancies as well as soaking up the gap that we have in the number of teachers."
Change emerging
Vice chair of the primary committee of the National Association of Headteachers, Angeles Walford - also head of a primary school in Wimbledon, London - said she had already noted a change.
Ms Walford said she had fewer children in reception classes compared with older years which were "bursting at the seams".
"I have got some classes of more than 30 but I've noticed there seems to be less children of reception ages," she said.
"As there are less of them it means they are getting a better deal and a better education.
"We haven't got enough teachers in this country at the moment and we're having to fill the posts with teachers from overseas which is costing a fortune."
A reduction in pupil numbers was good news as there may then be enough teachers and smaller class sizes, she added.
Planning ahead
A spokeswoman for the Department for Education said projections of declining numbers of under-16s had already been built into education plans for the next decade, although the figures could lead to "subtle" changes.
"We were already aware that the number of primary school children is starting to go down but there's no effect on the secondary school population yet," she said.
The impact of declining numbers on individual schools was something to be considered by local education authorities, she said.