I think it depends how messy she is and whether she will have hot school dinner and is a messy eater. Also, would you mind doing an extra wash during the week?
I bought six polos (two 3-packs), 4 trousers, 2 pinafores, 3 pairs of tights, 4 jumpers (warmer than cardigan in winter), 4 cardigans (better in Spring and Autumn), school shoes, trainers, plimsolls, 1 pair of PE shorts, 2 PE T-shirts, jogging suit for outdoor PE in winter, fleece, waterproof jacket (to be left at school), wellies (to be left at school), wintercoat.
At Easter I bought three Summer dresses, sandals and new plimsolls (outgrown the others).
Most of the clothes will still fit at least for the first half of next year, except the polos as they have shrunk.
It sounds like a lot (and it is a lot), but dd tends to get messy so we need new clothes for every day of the week plus I like her to have a complete set of spare clothes at school.