Parents are being forced to fork out hundreds of pounds for uniforms because schools have converted into academies, council leaders have warned.
Hundreds of schools are becoming academies each year, and mark the switch with new uniforms, but headteachers and governors need to consider the cost to families, according to the Local Government Association (LGA).
Conversion to academy status - which means that a school is free from local authority control and has freedom over areas such as the curriculum - often means that parents have to replace expensive items like blazers that are still in good condition, the LGA said.
It suggested that instead of introducing entirely new uniforms, new academies should keep costs to a minimum by using plain blazers that can have badges attached, or ensuring that items such as sports kit and school bags do not have to carry badges.
The LGA estimated that at least 275 schools will convert to academies at the beginning of the new term, while more than 100 are in the process of applying to become an academy.
This means that almost 400 schools could be changing their uniforms, the association suggested.
Councillor Nick Forbes, vice-chair of the LGA's children and young people board said: "Hundreds of schools are becoming academies every year and many choose to mark this change, but headteachers and governing bodies should think about the costs a new uniform can have on mums and dads.
"Parents already do what they can to cut the cost of school uniform, such as buying items of uniform throughout the year, passing clothes between children, shopping around to get the best deal and buying plain items they can sew badges onto, but the introduction of a new uniform can mean families are faced with having to pay hundreds of pounds all at once, to replace clothes which there is nothing wrong with.
"We want to see schools adopting a common sense approach to uniform policies, for example, by keeping to a similar colour scheme and allowing parents to buy new items gradually rather than all at once. Items like a blazer can be expensive, so we'd like to see schools let parents buy plain items they can sew or iron badges onto."
A Department for Education spokesman said: "We published guidance last year which states that schools should keep uniform costs to a minimum and prioritise value for money for parents. It also makes clear that schools should avoid frequent changes to uniform."