DD goes to an independent, so it might not be an accurate comparison -
Duffle coat - 105 (every 2 years)
Blazer - 95 (every 2 years)
Cagoule (sp?) - 30 (every 2 years)
2 x pinafore dress - 80 (every 2 years)
3 x polo necks - 60 (every 2 years)
School polo shirt - 14 (every year)
5 x unbranded polo shirts - 20 (they get grubby - every year)
Skort - 24 (every 2 years)
Shorts - 18 (ever 2 years)
2 x unbranded jogging bottoms - 12 (every year)
3 x unbranded cardigans - 18 (every year)
3 x summer dress - 68 (every 2 years)
1 x school jumper - 48 (every 2 years)
Ballet kit - 50 (every year)
Swimming kit - 35 (every year)
So around £400 per year. Plus socks, shoes, tights, trainers, etc. (let's say another £120 for those).
Most of the big ticket items we buy a little too big, and have them taken up, and down, as needed.
Where we can buy supermarket/unbranded (e.g. plain cardigans, plain polo shirts) we do.
There is a thriving 'nearly new' sale - and there is no shame in buying secondhand, many of the parents pass items between families as people grown in and out of them.