The cost of school uniform, sports kit and stationery supplies means parents are now spending £215 per child at the start of each school year, the research found.
With an average of two children in each family, that means £431 per year, or £5171 over the 12 years children are in school.
While parents in Scotland may spend more than the national average – which stands at £5033 for two kids over 12 years – those in Northern Ireland spend most cash (£6166), followed by London (£5559).
The cost of new school uniforms account for one-quarter of the cash spent each year – £52 for each child, closely followed by a new coat (£34) and school shoes (£33).
Amee Chande, managing director of the UK retail arm of Staples which carried out the study, said: "The list of things a child needs for the new school year can feel endless.
"As your children get older, there can be added pressure to spend more money than usual on a certain brand."