Unite said weighing children is a waste of public money and is not tackling the obesity crisis.
Unite calls for the employment of 2,000 school nurses, nearly double the current workforce, to monitor and give advice on the health of school children.
The call comes in the wake of new government statistics that said one in four children starting school is overweight or obese. This increases to one in three by the time children leave school.
Ros Godson, Unite professional officer for school-aged children, said: ‘We are appalled at this waste of money - which should be spent on helping families with overweight children - but is being frittered away in this expensive measuring exercise.’
Unite is calling on the government to ensure all 152 primary care trusts train ten new school nurses from September 2009.
The government has set a target date of 2010 for all secondary schools and its cluster of primary schools to have a nurse.