They aren't more expensive because they're better quality or made more ethically, they are expensive because it's a mini monopoly.
Our school supplier says this:
Ethical. At the School Uniform Shop all of our uniform is ethically sourced. This means that no child labour is used, working conditions are safe and hygienic, working hours are not excessive and regular breaks are implemented, wages are of the industry or country norm, employment is freely chosen, NO person will be taken against their will or forced to work and factories undergo rigorous checks and audits to make sure they are a safe and secure structure
Their polo shirts are £11-16 new.
You can also order from MyClothing (used to be Tesco school embroidery service). Their polo shorts start at £5.50. It says they’re “ethically sourced” and subscribe to the initiative H&M etc are signed up to.
Ethically, pretty sure the more expensive option is better if buying new.
But even better - and cheaper - is to buy secondhand. Pretty much all my DC’s school uniform is secondhand. Cheaper than the Asda/Tesco alternatives, and better for the planet.
I think all schools should be actively promoting secondhand and saying WHY.