As @Stinley says, even when I was in the UK, most state/public schools had moved to very affordable, simple uniforms. A navy (or grey/black/green) skirt, white shirt and jumper type thing. And you could buy clothes from ordinary stores rather than uniform shops.
In Australia, kids attending public/state schools may have formal uniforms with dresses and skirts/pants etc., but many kids just wear their sports uniform which is a pair of black microfibre shorts and a polo shirt with the school’s emblem on it. You can buy the shorts from Target. The shirts through the school or a local store and they’re cheaper than fashion clothing you’d buy from stores. They last for years. They’re hard wearing.
Kids attending private schools will usually have to wear a more formal (and expensive) uniform that might include blazers etc.
It would be interesting to hear where people are from. I’m seeing most people from the UK/Australia where uniforms for school are the norm seem to be supportive and in the US, where perhaps it’s not necessarily the norm (I’m not sure of this), people are opposed.