Children are at risk of being bullied because their parents struggle to pay for school uniforms available only from expensive suppliers, charities warn.
Schools can choose which uniform retailers to use
Research from insurer Norwich Union suggests families spent £1,300 a year on everyday school expenses - a rise of £200 over the last four years.
Charities including Barnardo's and End Child Poverty have called on ministers to promote "good practice" over costs.
The government said all schools were advised to make uniforms "affordable".
The charities said local authorities should check the impact of educational costs on families.
School governors should ensure uniforms were simple and available from more than one outlet, they added.
The Office of Fair Trading is conducting an inquiry into the trade after receiving complaints about high prices and poor quality.
It has written to 10,000 schools to find out whether their policy allows a choice of where to buy clothes.
Helen Dent, Chief Executive of the Family Welfare Association, which is a member of the coalition, said: "Expensive school uniforms cause worry for parents in low-income families and can leave their children feeling isolated and the target of bullies."
Citizens Advice chief executive, David Harker, said: "No child's education should be damaged by their inability to afford specific uniforms, or the many other costs such as trips that parents incur."
The Welsh Assembly launched a uniform grant scheme in 2005, offering £95 for all 10 to 11-year-olds entitled to free school meals.
In England, the school clothing market is thought to be worth about £450m a year, with most state pupils having to wear uniforms.
A Department for Education and Skills spokesman said: "Our clear guidance to schools is that they ensure that any uniform policy is affordable - our most recent survey showed 89% of parents were in favour of uniforms and 85% were happy with the cost.
"Our guidance also makes clear that parents' views are considered and that inappropriate sanctions are not used against pupils whose parents' cannot afford particular items of uniform.
"School uniforms help to define the ethos of a school and can help improve behaviour and attendance."
The group of charities consists of: Barnardo's, Child Poverty Action Group, Citizens Advice, End Child Poverty, the Family Welfare Association, One Parent Families and Save the Children.
The National Union of Teachers is also backing the campaign.