Schools are to join airlines, power stations and supermarkets in trading carbon, under British government plans to tackle global warming to be announced on Wednesday. Hilary Benn, environment secretary, will say that pollution from state schools is to be included in a scheme that will force hotels, universities and other medium sized organisations to buy and sell carbon permits. The government says the scheme will be financially neutral overall, with those bodies who cut their emissions being rewarded and those who overshoot their allowances being forced to buy extra permits.