The seven-year countdown to the London Olympics will revitalise school sports and provide a unique opportunity to tackle spiralling levels of childhood obesity, experts said last night.

Headteachers and union leaders said tens of thousands of schoolchildren would be inspired to take up sport and ministers insisted they would "do all they could to make the pathway from the playground to podium a reality".

In the run-up to the bid, officials repeatedly stressed that the Games would leave a lasting legacy for young people.

Speaking after the result, Tessa Jowell, newly created minister for the Olympics, said that would not change: "When we were waiting for the final result there were 30 kids from a London school representing 20 different nationalities. We asked them, 'How many of you are going to go for gold medals?' They all put up there hands.

"That's what this is for - this is to unlock their ambition and make it worth their dreaming. Sport will be completely central to government policy."

Among the group were youngsters from Langdon school, a specialist sports college in the London borough of Newham.

Last night, headteacher Vanessa Wiseman said the decision had transformed the sporting and social prospects for thousands of young people.

"It was an amazing moment in school when the announcement was made. There was a great cheer and the children were absolutely ecstatic. It has made them all so proud."

She added: "This puts sport right at the top of the agenda. We will have great facilities, wonderful coaches and, above all, that fantastic psychological lift which means sport and everything around it will be incredibly exciting."

Teachers leaders agreed the decision would have a major impact on future generations.

"This will inspire our children," said Steve Sinnott, general secretary of the National Union of Teachers. "Sport is so important, fitness is so important to the wellbeing of our children and our country. It is a magnificent achievement. The benefits will be felt most in the East End of London but will accrue to the whole country."

John Dunford, general secretary of the Secondary Heads Association, said he was delighted. "It will give a big boost to school sport," he said. "It offers leading sportspeople the opportunity to become role models for future generations."

The government says all pupils should complete a minimum of two hours' PE and sport a week by 2010 and says it is investing £1.5bn in school sports between 2003 and 2008.

A spokesman for the Department for Education and Skills (DfES) said many of the stars of 2012 were still at school and insisted the government would do all it could to help them fulfil their potential.

London's victory was also welcomed by health campaigners. David Haslem, chairman of the National Obesity Forum, said the Olympics would prove a catalyst for a "step change" in the health of a generation.

"This really offers an amazing chance to galvanise people in the fight against childhood obesity and other diseases. It will change the environment in terms of facilities and, more importantly, it will put sport at all levels right at the top of the agenda."

About 10% of six-year-olds are obese, with the figure rising to 18% among 15-year-olds, he said.

"Children want to run around and be active and now everything will be focused on that with more schools taking an interest in sport and more children signing up to join clubs. This really is fantastic news for the health of young people."

Ms Wiseman said: "Everybody right across the school is thrilled, I think they are really proud of being Londoners today wherever they or their families are from."

She said the Olympics would be especially inspiring for those children not directly involved in sport.

The government says it is also planning to upgrade facilities and staffing levels to give young people the chance to take part in a further two to three hours of sport outside school hours.

"We are creating 400 specialist sports colleges and 400 school sport partnerships to deliver improved sporting opportunities; dedicated sports training for teachers; create young leaders and sports volunteers; and build effective links between schools and sports clubs," said a spokesman for the DfES.