DD is 16.
After primary the big items were school uniform, phone, laptop and school books.
Clothes/shoes as soon as she started adult sizes, in her case, when she was 12. And she has no interest in brands.
Books - I just spent £100 on 6th form books with lots more to come. When she started GCSE in Y10 I think I paid around £500 for school books and revision workbooks/guides.
Pocket money - nowadays it is virtually impossible to get a job under 16 unless you have some connections. We live in a town with a college and most jobs are taken by the students as they are over 18 and you don't have the red tape to employ them.
Clubs are obviously a personal choice, we pay around £200/term for theatre, scouts, Tae-kwon-do and riding.
Eating out - normal adult portions
Holiday - either a proper 2 bedroom appartment or a second hotel room
"Luckily" she had no school trips thanks to Covid.
We put £250/month aside since 5 years to hopefully be able to get her to go to uni without huge student debt. That is extra to any savings we do for other things. Her grandparents are saving for driving license, car and after uni life.
And we only have one child.