The average annual cost, including uniforms, coats, bags and stationery, is now £156 for a child at primary school and £285 for a child at secondary school, the report by Family Action found.
Items that some schools are requiring parents to buy for their children include £98 coats, £89 blazers, £38 rugby shirts and £27 jumpers.
Compulsory items, many of which can only be bought at expensive specialist shops, include jogging bottoms with the child's initials printed on them, aprons for cookery classes, and even straw boaters, the charity claims.
It said some schools expect pupils to have a summer uniform as well as a standard one, while others demand a range of branded sports wear.
It also claims parents of larger children have to pay nearly twice as much for larger size uniforms than they would for smaller sizes.
According to the report, the majority of secondary schools expect parents to spend between £200 and £300, yet parents of pupils at some schools are expected to fork out up to £600 per child.
Other costs that schools expect parents to meet include textbooks, workbooks, art and craft materials, school trips and outings, and sometimes iPads.
Meanwhile, local authority grants for school uniforms are a patchy postcode lottery, with many having scrapped their schemes completely, the charity found.
It is calling on schools to scrap specially-branded uniforms entirely and let parents shop around for plain, standard clothing from a retailer of their choice, and introduce sew-on badges, sold separately and at cost price.
Family Action chief executive David Holmes said: "This report shows that the cost of sending children back to school every September is becoming prohibitive for many families on low incomes.
"It's not just the case of a badge and a jumper - these days schools expect blazers, summer and winter uniforms, and branded sportswear. We've even seen cases of aprons, boater hats and iPads being demanded.
"With local authority grants schemes offering only patchy financial support, parents are left to make very difficult choices about what items they can afford and what they have to sacrifice.
"The fairest solution is to change the whole way we approach school uniforms. Let families buy good value plain clothes from a supermarket and add a school logo to them later."