County Durham teachers say government cuts to a programme supporting school sport could damage efforts to encourage children to be healthy and active.
They are angry that an annual £162m for 400 school sport partnerships around England will be axed from next year.
Partnerships fund extra PE sessions and give pupils a chance to try out sports like tag rugby, golf and climbing.
Ministers claim sport partnerships are "unaffordable" and individual schools must foot the bill from 2011.
Dianne Snowsill, of Sedgefield School Sport Partnership, said the proportion of pupils doing two hours of physical education a week in local schools had increased from 23% to 90% in recent years.
She said: "As we build up to the Olympics and Paralympics, we were building up to a huge crescendo to get more children involved.
"Now the rug has been pulled from under our feet."
The Department for Education has said central funding of school sport partnerships is no longer viable and that schools must decide if they want to fund them once Whitehall funding is ended next year.
Among the government's alternatives is a new "School Olympics," which will be piloted in Tyne and Wear next year and launched nationwide in 2012.
But Judith Reeves, head teacher of St Charles' Catholic Primary School in Spennymoor, said she feared her school would miss out on the extra support it currently gets from its local partnership.
She said: "If you cut the funds centrally you are going to cut the opportunities we give the children.
"It will mean we won't be able to get the support of high quality coaches. We will not be able to take part in festivals and competitions."
See more on this story in The Politics Show on BBC1 on Sunday at 1530 GMT.